| 1. |
- Zhao, Xin, 1986, et al.
(författare)
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Experimental Validation of the Aerodynamic Characteristics of an Aero-engine Intercooler
- 2017
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 139:5
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Tidskriftsartikel (refereegranskat)abstract
- Porous media model computational fluid dynamics (CFD) is a valuable approach allowing an entire heat exchanger system, including the interactions with its associated installation ducts, to be studied at an affordable computational effort. Previous work of this kind has concentrated on developing the heat transfer and pressure loss characteristics of the porous medium model. Experimental validation has mainly been based on the measurements at the far field from the porous media exit. Detailed near field data are rare. In this paper, the fluid dynamics characteristics of a tubular heat exchanger concept developed for aero-engine intercooling by the authors are presented. Based on a rapid prototype manufactured design, the detailed flow field in the intercooler system is recorded by particle image velocimetry (PIV) and pressure measurements. First, the computational capability of the porous media to predict the flow distribution within the tubular heat transfer units was confirmed. Second, the measurements confirm that the flow topology within the associated ducts can be described well by porous media CFD modeling. More importantly, the aerodynamic characteristics of a number of critical intercooler design choices have been confirmed, namely, an attached flow in the high velocity regions of the in-flow, particularly in the critical region close to the intersection and the in-flow guide vane, a well-distributed flow in the two tube stacks, and an attached flow in the cross-over duct.
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| 2. |
- Hartono, Erwin Adi, 1986, et al.
(författare)
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A PIV Study of The Cooling Air Flow in An Electric Generator Model
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- One factor that affects the performance of a hydro power generatoris temperature. The efficiency, the electric resistance, the cables, thewindings, etc, are temperature-dependent. These make controllingtemperature rise in a generator of high importance in order to minimizehot spots and material failure. In order to tackle the problem airis used as a cooling fluid, which circulates through the stator and rotorin the generator.A generator model has been specially designed to perform fluid flowmeasurement. 2D-2C PIV (Two Dimension - Two Component ParticleImage Velocimetry) was used to measure the fluid velocity inside thestator channels. Stereo PIV (2D-3C) was used to measure fluid velocityoutside of the stator body.The results show that the tangential velocity component dominatesthe flow outside the stator. Inside the stator channels the fluid movesradially with a large recirculation region (almost half of the channelwidth) behind the coil. The flow structure inside the channels is shownto be independent of the rotor pole position.
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| 3. |
- Hartono, Erwin Adi, 1986
(författare)
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Experimental Study on Truck Related Power Losses: The Churning Losses in a Transmission Model and Active Flow Control at an A-pillar of Generic Truck Cabin Model
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The fight with global warming constantly forces vehicle manufacturers to innovate, in order to be able to reduce the CO2 emissions of their product. This means that marginal efficiency gains in every component are considered beneficial for total reduction of CO2 emissions. For long-haul heavy-duty trucks, the transmission losses and the aerodynamic drag are two of the important losses. If we look at the truck transmission, the losses in form of churning losses stems from the interaction between oil and partially immersed rotating gear wheel. It is obvious that reducing the amount of oil inside the transmission lower the churning losses. However, the presence of oil inside a transmission is not solely for lubrication purposes but also for heat dissipation. Excessive heat on the components impacts greatly on their durability / lifetime. Finding a balance between low loss and high heat dissipation requires further studies in the area of fluid dynamics. In this study, oil flow inside a transmission was studied by means of flow visual- ization, velocity measurement, and torque measurement. A simplified version of a transmission was specially built to be able to study in more detail the oil flow inside the gearbox. The test section, test object, and test oil have clear appearance for ensuring good optical access. Flash photography and high speed recording were used to visualize the oil flow. Particle image velocimetry was used to measure the oil flow velocity. The torque loss was measured for different oil level and gear geometry. The torque loss estimation formula was fitted with the help of machine learning algorithm in search of general equation that described the churning losses. The results shows that rotational speed, immersion depth and geometry have dominant effect to splash pattern and oil distribution inside the transmission. The 2C2D-PIV measured the oil flow velocity in the mid-plane and revealed recirculation regions below the gear and the pinion. The 3C2D-PIV was done in several different planes and reconstruction of the data shows the three dimensional flow below the gear wheel. Cross plane measurement revealed vortices below the gear wheel and oil flow velocity in the gear meshing region. Air entrainment into the oil sump (aeration) was observed during the measurement. Aeration was caused by solid and liquid impingement to the free surface. The aeration level was estimated up to 20%. Torque measurement shows up to 9% increase in torque was found when comparing torque data between aerated and non-aerated oil. Curve fitting to the torque measurement data was done with help of machine learning algorithm. If we look at the truck aerodynamics drag, it stems from flow separation. Trucks are considered as a bluff body from fluid dynamics perspective. The aerodynamic drag of a bluff body is dominated by the pressure drag, which is the pressure difference between the stagnation point and the wake. The earlier the flow separate from the body, the larger the wake size. There are several locations in the truck where the flow separates. The front of the truck, the A-pillar, the under-body and the wheel, the gap between tractor and trailer, and the wake behind the trailer. In this study, flow separation at the A-pillar was investigated. An active flow control in term of zero net flux synthetic jets was applied. The synthetic jets role were to energize the boundary layer which in return suppress the flow separation. The study was performed in a generic truck cabin model specially build for this study. The measurements were done at Chalmers wind tunnel with inlet velocity of 20 m/s. Combining the inlet speed with the 0.4 m characteristic length of the model, the resulting Reynolds number was 5 × 105. Pressure measurement and velocity measurement using time-resolved PIV were done to quantify the flow velocity field with and without the active flow control at the side and at the wake region of the test object. Four different actuation cases (F + = 1, 2.1, 3.1, and 6.2) of the synthetic jet are studied and measured. Hot wire anemometry was used to characterize the actuators that produce the synthetic jet. The results suggest that the receptive band of the shear layer and wake in this study was in the range between 0.7 < F+ < 3.1. The chosen F+ value of 1, 2.1, 3.1, and 6.2 successfully showed suppression of the flow separation at the A-pillar. The F+ = 1 shows the lowest absolute streamwise velocity and the shortest wake. The F+ = 2.1 and 3.1 show a lower base pressure region and a very similar wake configuration. The strongest level of flow separation suppression happened at F+ =3.1 . The F+ = 6.2 was chosen to confirm previous study that the velocity fields in the wake becomes independent from the actuation frequency. The experimental data gathered in this study were proven to be useful and were used to validate a numerical simulation. The experimental data from the churning losses study were used to validate a numerical method, smoothed particle hydrodynamics. The data from active flow control study were used to validate CFD simulation using PANS turbulence model. Additional knowledge to the fields of fluid dynamics especially in oil flow around a spur gear inside a transmission and active flow control using synthetic jets for A-pillar were added. The work has laid a good foundation for future study in these topics.
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| 4. |
- Hartono, Erwin Adi, 1986, et al.
(författare)
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PIV Measurement of Air Flow in a Hydro Power Generator Model
- 2012
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Ingår i: 16th Int Symp on Applications of Laser Techniques to Fluid Mechanics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cooling of electrical generators is of high importance since an uncontrolled temperature rise can lead toformation of hot spots which can cause material failure. The efficiency of the machines in converting themechanical energy to electricity is also affected by temperature, as the electric resistances of the cables andwindings are temperature dependent. In order to tackle the problem, air is used as a cooling fluid, whichcirculates through the stator and rotor in the generator. Despite the fact that electrical generators have beenused for many years, the knowledge about the cooling air flow inside them is still limited. Understanding theair flow inside the generators leads us into better predictions of heat transfer. The knowledge is alsoimportant when modifying the stator and rotor shapes, or when innovating new air cooling systems.In this work, a generator model has been specially designed to perform fluid flow measurement. RapidPrototyping was used to build the model due to its capability to create complex geometries in good accuracyin a short time.Planar two-component Particle Image Velocimetry (2D-2C) was used to measure the fluid velocity insidethe stator channels. A section of the stator was built in fully transparent material, to give optimal opticalaccess. The flow path inside the channels was small and thus the optical view was prone to light scatteringand reflection from the walls. A marker paint was used to paint the channel walls black, leaving just onetransparent wall. A special dummy channel without coils and baffles was manufactured, for use whenmeasuring in the middle channel rows.Stereo PIV (2D-3C) was used to measure the fluid velocity outside the stator body. In total 15measurement planes were created to capture the overall picture of the flow. This data was then interpolatedto get an overview of the flow field around the stator body.The results show that the tangential velocity component dominates the flow outside the stator. The flowoutside is highly swirling and three-dimensional. Inside the stator channels the fluid moves radially withlarge recirculation region (almost half of the stator channel width) behind the coil. Phase-averagedmeasurements show that the flow structures inside the channels are independent of the rotor pole position.
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| 5. |
- Hartono, Erwin Adi, 1986, et al.
(författare)
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PIV Study of Fluid Flow inside a Gearbox
- 2013
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Ingår i: PIV13; 10th International Symposium on Particle Image Velocimetry, Delft, The Netherlands, July 1-3, 2013.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- For dip lubrication system, simple act of reducing the amount of lubricant inside the gearbox can reduce the load-independent losses but at the same time reduce the lifetime of the gear itself due to increasing bulk temperature [1]. Finding a proper lubricant level require understanding of the lubricant flow inside a gearbox. Therefore, 2D-2C PIV of a gearbox model has been done to study more detail the flow. The measurements were taken at three different lubricant levels (centreline, two module of gear, two module of pinion) and three different pitch line velocities (0.6, 1.1, and 1.62 m/s). Viscosity of the test oil (Nytex 810) is maintained at approximately 64 cSt by maintaining temperature at 20°C. The results suggest that flow inside a gearbox is complex, three dimensional and involves effects of rotation, inertia, free-surface dynamics, formation of bubbles and droplets, and also phenomenon of laminar-turbulent transition.
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| 6. |
- Hartono, Erwin Adi, 1986, et al.
(författare)
-
Stereo-PIV Study of Oil Flow Inside a Model Gearbox
- 2014
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Ingår i: 17th Lisbon International Symposium On Applications of Laser Techniques to Fluid Mechanics. ; , s. 8-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Hartono, Erwin Adi, 1986
(författare)
-
Study of fluid flow inside the gearbox
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Long haul trucks spend (almost) 80% of their time cruising from one destination to another. This means that they drive mostly at a constant speed and use their top gear most of the time. Depending on the gearbox, the top gear of long haul trucks is usually direct drive gear. With the direct drive gear losses mainly come from the interaction between lubricant and rotating gear (churning losses). It is obvious that using a small amount of low viscosity lubricant will reduce the churning losses dramatically. Unfortunately the solution is not as simple as that. This is because, besides lubrication, the lubricant is also there as a cooling agent. Hence, too little oil will affect the heat dissipation and the lifetime of the gear. Studies of oil flow inside the gearbox are needed to find ways to reduce churning losses and good heat dissipation.A simplified version of a gearbox is built to study the flow, due to the complexity of the real gearbox. The new gearbox consists of a gear pair and has transparent rectangular walls to ensure good optical access. Velocity measurements with particle image velocimetry (PIV) are made to get the velocity field around the gear. Flash photography is done, as additional data, to study the flow distribution. Finally, torque measurements are made to measure the losses.It was found in the PIV study that oil flow is dominated by a recirculation region. The recirculation is suspected to be the source of viscous losses. The oil flow inside the gearbox is highly three dimensional. Stereo-PIV has successfully revealed the third components of the flow. PIV measurements also reveal that the squeezing of the oil at the gear contact is considered minor compare to the losses due to recirculation. From flash photography, the splash pattern and oil distribution is studied. The oil distribution inside the gearbox is governed by a gear with a larger diameter. The larger diameter gear splashes more oil compared to the smaller one. This is most probably because the larger diameter gear is more immersed compared to the smaller diameter gear. Hence, the larger diameter gear drags more oil upward. Torque measurements show that the torque is dependent on the rotational speed, the immersion depth, and the oil properties. The oil properties are suspected to be changed when the oil is aerated, resulting in a higher torque reading.
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| 8. |
- Hartono, Erwin Adi, 1986
(författare)
-
Svenska mekanikdagar 2013
- 2013
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Ingår i: Svenska mekanikdagar 2013.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Gearbox is an essential element in power transmission. Efficient gearbox means efficient power transmission. Hence lower energy consumption. Losses in the gearbox can be sorted into two; load-dependent and load-independent losses. Load-dependent are related to friction, and load-independent losses are mainly related to lubricant. Load-independent losses are the focus of this paper.An experimental rig (Chalmers gearbox rig) based on the FZG gear test rig was built. The test gears have a slight gap in between the mate teeth and are driven by slave belt and in order to eliminate contact (friction). The idea is to get pure load-independent losses. Flow visualization study was chosen as a first method to study oil flow inside a gearbox. A set of external flash and a camera were used to capture instantaneous splashes in different pitch line velocity and different oil level. Hydrotreated process oil was used due to its transparency. The temperature of the oil was maintained at 40°C to match the viscosity of Castrol Syntrans 75W-85 at 90°C. Understanding the splash behavior are essential in order to understand the flow phenomena and to be able to study the flow further with more advance method, such as computational fluid dynamics (CFD) or particle image velocimetry (PIV).
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| 9. |
- Ji, Zhe, et al.
(författare)
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Numerical simulations of oil flow inside a gearbox by Smoothed Particle Hydrodynamics (SPH) method
- 2018
-
Ingår i: Tribology International. - : Elsevier BV. - 0301-679X. ; 127, s. 47-58
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, numerical simulations of oil flow inside a gearbox are presented and compared to experimental particle image velocimetry (PIV) results. Instead of a traditional grid-based finite volume method, a mesh-free Smoothed Particle Hydrodynamics (SPH) method is employed. A multi-phase SPH formulation is utilized to resolve the complex multiphase fluid flow. A total of nine simulations are carried out for three oil levels and three Reynolds numbers, to investigate the flow field behavior and to compare with the experimental results. The aeration effect is first considered to qualitatively analyze the quantity and size of bubbles generated due to the rotation of the gears. Furthermore, the velocity field and velocity profile beneath the oil surface are comprehensively analyzed. Our simulation results exhibit physically consistent behavior of the oil flow and good agreement is achieved compared to the experimental results. Flow structures, splashing and recirculation areas are very well captured by the simulation. However, some discrepancies of the velocity field between the numerical and experimental results are also observed, and discussed.
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| 10. |
- Mastrone, Marco Nicola, et al.
(författare)
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Oil distribution and churning losses of gearboxes: Experimental and numerical analysis
- 2020
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X. ; 151
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Tidskriftsartikel (refereegranskat)abstract
- Currently, energy efficiency represents one of the main requisites in mechanical design. Gearboxes play an important role in several industrial applications and, even if they are already characterized by high efficiency, their performance can still be improved, leading to energy saving and the reduction of pollutant emissions. The possibility to investigate different gearbox geometries and operating conditions in the preliminary stages of design represents a clear advantage for engineers and can significantly contribute to the achievement of these objectives. However, analytical formulations that are able to accurately describe gear losses, especially those due to the interaction with the lubricant, are not available or are not accurate enough. Furthermore, the analytical models are typically not suitable for novel gearbox designs. In the present work, a numerical approach based on Computational Fluid Dynamics (CFD) for the prediction of lubricant fluxes and power losses of gearboxes is presented. The presented methodology utilizes a meshing strategy that reduces the computational effort of the simulations and enables parametrical studies. The numerical approach is validated both with torque measurements and data regarding the oil flow obtained by the Particle Image Velocimetry (PIV). Thus, the validation of the numerical approach is performed not only qualitatively with respect to the oil distribution but also quantitatively with respect to the torque and velocity field in the oil sump. Good agreement of the CFD and experimental data was observed for the torque, oil distribution and fine flow details including the vorticial structures and recirculation areas.
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| 11. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Aerodynamic flow control for a generic truck cabin using synthetic jets
- 2017
-
Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 168, s. 81-90
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Tidskriftsartikel (refereegranskat)abstract
- This experimental work presents the achievement in drag reduction with the use of active flow control (AFC) for a generic bluff body. Experiments were done in the Chalmers University closed loop wind-tunnel at Reynolds number . The is based on the undisturbed velocity m/s and the width of the model m. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the rounded vertical side edges. The pressure induced separation reproduces the flow detachment occurring at the front A-pillar of a real truck. The investigation of the unactuated and actuated flow was conducted by means of time-resolved particle image velocimetry (PIV). Loudspeakers were used as the actuation device. These were characterized before the actuation study, highlighting an interesting analogy between actuation frequency and jet vortex pair size. The effects of different actuations were evaluated with hot wire anemometry. The effect of the actuation was studied using phase averaging and modal analysis. A notable reduction of the side recirculation bubble was observed. The nature of the separation mechanism was investigated and related to different actuation frequencies spanning the range . As for the , the non-dimensional frequency is based on the undisturbed velocity and the width of the model W.
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| 12. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Development of Active Flow Control for Trucks
- 2018
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Ingår i: Proceedings of the Thermal and Fluids Engineering Summer Conference. - 2379-1748. ; 2018-March
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Konferensbidrag (refereegranskat)abstract
- The possibility to actively control the external aerodynamic of vehicles is an attractive yet challenging solution to decrease the aerodynamic drag and the fuel consumption. The work flow that describes the implementation of an Active Flow Control (AFC), for the suppression of the separated flow at the A-pillar of a truck, is summarised in this paper. The presented work spans from a theoretical verification of the method to a preliminary implementation of an AFC on a real full-scale truck cabin. The study involves numerical (CFD) and experimental work, including aerodynamic test in a full scale wind tunnel. The initial CFD simulations of a simplified A-pillar were performed using turbulence resolving numerical method large-eddy simulations (LES). A second step consisted in simulation of a simplified truck cabin using hybrid Partially-Averaged Navier-Stokes simulations (PANS). The AFC was created using synthetic jets produced by the use of loudspeakers mounted in the A-pillars of the model. The numerical and experimental investigations were used to optimise the actuation parameters leading to maximum drag reduction. The final step of the validation of the AFC concept was achieved with a full scale test experimental campaign of a Volvo Truck cabin equipped with the studied AFC device.
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| 13. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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EXPERIMENTAL AND NUMERICAL INVESTIGATION OF ACTIVE FLOW CONTROL ON A GENERIC TRUCK CABIN
- 2016
-
Ingår i: 11TH INTERNATIONAL ERCOFTAC SYMPOSIUM ON ENGINEERING TURBULENCE MODELLING AND MEASUREMENT.
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Konferensbidrag (refereegranskat)abstract
- This work presents the achievement in drag reduction by use of Active Flow Control (AFC) on a generic bluff body. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the rounded vertical front corner. The pressure induced separation reproduces the flow separation occurring at the front A-pillar of a real truck.Hybrid Partially Averaged Navier-Stokes (PANS) simulations are compared with wind tunnel experiments.The Reynolds number for both simulations and experiments is Re = 5×10^5 based on the inlet velocity Uinf and the width of the model W = 0.4 m. A validation of the hybrid CFD model on two flow configurations is followed by a CFD study on the optimal actuation frequency able to minimize the aerodynamic drag. PANS accurately predicts the flow field measured in experiments and a notable drag reduction by means of AFC is observed in a numerical study.
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| 14. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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FLOW CONTROL FOR A GENERIC TRUCK CABIN USING SYNTHETIC JET
- 2017
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Ingår i: European Drag Reduction and Flow Control Meeting – EDRFCM 2017 April 3–6, 2017, Rome, Italy.
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Konferensbidrag (refereegranskat)abstract
- Active flow control can be applied using a various number of approaches. The general, yet ultimate, goal is to use a control strategy able to actively manipulate a separated flow.Reattachment or deflection of the shear layer is of main importance to enhance the aerodynamic performance of blunt and aerodynamic bodies. The experiments presented in this paper show the achievements of a synthetic jet used to mitigate and eventually suppress the recirculation bubble occurring at the A-pillars of a truck, Fig. 1a. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the rounded vertical front corners. The pressure induced separation reproduces the flow detachment occurring at the front A-pillars of a real truck. Figures and dimensions of the model are presented in Figs. 1 (b and c), 2, and Tab. 1, respectively. Time resolved PIV was employed to investigate the flow (Re = 5 × 10 5 ), Fig. 3. The snapshots were post processed using modal and phase averaged analyses.
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| 15. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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PANS Validation and Active Flow Control for a Simplified Truck Cabin
- 2017
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Ingår i: 16th European Turbulence Conference, 21-24 August, 2017, Stockholm, Sweden.
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Konferensbidrag (refereegranskat)abstract
- Active Flow Control (AFC) can be applied using a various number of approaches. The general, yet ultimate, goal is to use a control strategy able to actively manipulate a separated flow. Reattachment or deflection of the shear layer is of main importance to enhance the aerodynamic performance of blunt and aerodynamic bodies. The paper presents a numerical and experimental study of the suppression of the recirculation bubble occurring at the side of a generic truck cabin (A-pillar separation) at Re = 5 × 10 5 . In this work the hybrid Partially Averaged Navier-Stokes (PANS) method was used.The aim of the present study is twofold: to validate the PANS method against in-house experiments and a resolved LES simulation, and to simulate the effect of an AFC on a heavily separated turbulent flow. Figure 1 shows the dimension of the computational and experimental domains (a and b) and the observed window in both experiments and simulations (c and d). The results show a good flow prediction by PANS even when the computational domain is drastically coarsened, Fig. 2. Velocity and Reynolds stress profiles, as well as modal and frequency analysis will be compared for a full validation.The AFC effect shows a drastic decrease of the side recirculation bubble, Fig. 3. The separation is observed to be receptive to the control and it locks to the specific actuation frequency when the latter is in the "receptive band". The flow reaches a frequency independent behaviour when the actuation frequency exceeds this range.
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| 16. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Validation of PANS and active flow control for a generic truck cabin
- 2017
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 171, s. 148-160
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a drag reduction study using active flow control (AFC) on a generic bluff body. The model consists of a simplified truck cabin, characterized by sharp edge separation on top and bottom edges and pressure induced separation on the two other rounded vertical front corners. The pressure induced separation reproduces the flow detachment occurring at the front A-pillar of a real truck (Schuetz, 2015). The prediction of the flow field by partially averaged Navier-Stokes (PANS) simulations, conducted on a relatively coarse mesh, is validated against wind tunnel data (pressure measurements and particle image velocimetry (PIV)) and resolved large eddy simulations (LES) data. The Reynolds number for both simulations and experiments is Re=5×10^5 (which corresponds to 1/6 of a full scale truck Re) based on the inlet velocity Uinf and the width of the model W=0.4m. A validation of PANS results is followed by a CFD study on the actuation frequency that minimizes the aerodynamic drag and suppresses the side recirculation bubbles. PANS accurately predicts the flow field measured in experiments and predicted by a resolved LES. The side recirculation bubble of a simplified truck cabin model is suppressed almost completely and a notable drag reduction by means of AFC is observed.
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