| 1. |
- Okda, Sherif, et al.
(författare)
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Testing of the Aerodynamic Characteristics of an Inflatable Airfoil Section
- 2020
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Ingår i: Journal of Aerospace Engineering. - 1943-5525 .- 0893-1321. ; 33:5
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Tidskriftsartikel (refereegranskat)abstract
- Inflatable structures are characterized by being light and easy to manufacture and deploy. Hence, they find many applications in aerospace and aeronautical engineering. In this paper, an inflatable segment with a The National Advisory Committee for Aeronautics (NACA) 0021 airfoil cross-section is designed, fabricated, and tested. The geometrical accuracy of the manufactured inflatable segment is measured using laser scanning. Measurements show that the average normalized error of the chord length and thickness are 2.97% and 0.554%, respectively. The aerodynamic behavior of the inflatable segment is then tested in a wind tunnel at different wind speeds and angles of attack. Lift forces are measured using a six-component balance, while the drag forces are calculated from the wake measurements. The lift and drag coefficients of the inflatable section are compared to those of a standard NACA 0021 airfoil. Finally, flow visualization is examined at different angles of attack using two methods: smoke and tufts. Both methods show that flow separation starts at 15° and full stall occurs at 25°. Results indicate that inflatables can find more applications in the design and construction of aerodynamic structures, such as wings.
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| 2. |
- Chernoray, Valery, 1975
(författare)
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Prediction of Laminar-Turbulent Transition on an Airfoil at High Level of Free-Stream Turbulence
- 2015
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Ingår i: Progress in Flight Physics Vol. 7. - 9785945881655 ; , s. 704-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Prediction of laminar-turbulent transition at high level of free-stream turbulence in boundary layers of airfoil geometries with external pressure gradient changeover is in focus. The aim is a validation of a transition model for transition prediction in turbomachinery applications. Numerical simulations have been performed by using a transition model by Langtry and Menter for a number of different cases of pressure gradient, at Reynolds number-range, based on the airfoil chord, 50 000 ≤ Re ≤ 500 000 and free-stream turbulence intensities 2 % and 4 %. The validation of the computational results against the experimental data showed good performance of used turbulence model for all test cases.
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| 3. |
- Chernoray, Valery, 1975
(författare)
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Prediction of Laminar-Turbulent Transition on an Airfoil at High Level of Free-Stream Turbulence
- 2013
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Ingår i: Proc of EUCASS Conf..
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Konferensbidrag (refereegranskat)abstract
- Prediction of laminar-turbulent transition at high level of free-stream turbulence in boundary layers of airfoil geometries with external pressure gradient changeover is in focus. The aim is a validation of a transition model for transition prediction in turbomachinery applications. Numerical simulations have been performed by using a transition model by Langtry and Menter for a number of different cases of pressure gradient, at Reynolds number-range, based on the airfoil chord, 50 000 ≤ Re ≤ 500 000 and free-stream turbulence intensities 2 % and 4 %. The validation of the computational results against the experimental data showed good performance of used turbulence model for all test cases.
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| 4. |
- Niebles Atencio, Bercelay, 1979, et al.
(författare)
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An experimental study on laminar-turbulent transition at high free-stream turbulence in boundary layers with pressure gradients
- 2012
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Ingår i: The European Physical Journal Conferences. - : EDP Sciences. ; 25, s. Art. no. 01012-
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Konferensbidrag (refereegranskat)abstract
- We report here the results of a study on measurements and prediction of laminar-turbulenttransition at high free-stream turbulence in boundary layers of the airfoil-like geometries with presence of the external pressure gradient changeover. The experiments are performed for a number of flow cases with different flow Reynolds number, turbulence intensity and pressure gradient distributions. The results were then compared to numerical calculations for same geometries and flow conditions. The experiments and computations are performed for the flow parameters which are typical for turbomachinery applications and the major idea of the current study is the validation of the turbulencemodel which can be used for such engineering applications.
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| 5. |
- Wang, Chenglong, et al.
(författare)
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An Experimental Study of Heat Transfer on an Outlet Guide Vane
- 2014
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Ingår i: ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, GT 2014; Dusseldorf; Germany; 16 June 2014 through 20 June 2014. - 9780791845721 ; 5B, s. UNSP V05BT14A001-, s. 001-14
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Konferensbidrag (refereegranskat)abstract
- In the present study, the heat transfer characteristics on the suction and pressure sides of an outlet guide vane (OGV) are investigated by using liquid crystal thermography (LCT) method in a linear cascade. Because the OGV has a complex curved surface, it is necessary to calibrate the LCT by taking into account the effect of viewing angles of the camera. Based on the calibration results, heat transfer measurements of the OGV were conducted. Both on- and off-design conditions were tested, where the incidence angles of the OGV were 25 degrees and -25 degrees, respectively. The Reynolds numbers, based on the axial flow velocity and the chord length, were 300,000 and 450,000. In addition, heat transfer on suction side of the OGV with +40 degrees incidence angle was measured. The results indicate that the Reynolds number and incidence angle have considerable influences upon the heat transfer on both pressure and suction surfaces. For on-design conditions, laminarturbulent boundary layer transitions are on both sides, but no flow separation occurs; on the contrary, for off-design conditions, the position of laminar-turbulent boundary layer transition is significantly displaced downstream on the suction surface, and a separation occurs from the leading edge on the pressure surface. As expected, larger Reynolds number gives higher heat transfer coefficients on both sides of the OGV.
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| 6. |
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| 7. |
- Jonsson, Isak, 1990, et al.
(författare)
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Infrared thermography investigation of heat transfer on outlet guide vanes in an engine exit module
- 2019
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Ingår i: 13th European Turbomachinery Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2019.
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Konferensbidrag (refereegranskat)abstract
- This paper presents experimental results of heat transfer coefficient on an outlet guide vane (OGV) in an engine exit Module (EEM) at engine-representative conditions. The results were obtained in Chalmers OGV-LPT test facility with a newly developed method to measure heat transfer with high accuracy that is applicable to a large variety of geometries. A thin-walled OGV was manufactured with an internal water heating system and surface temperature was measured by IR thermography. An extensive effort has been made to mitigate all major sources of uncertainty and results from three different load cases at Reynolds number 235000 is presented. The current study is closing the gap which previously existed in the literature by providing data on heat transfer on EES OGVs under engine representative conditions. These results are crucial for designing future high-bypass ratio aero-engines which is a new radical concept requiring improvement of the existing design of EEMs.
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| 8. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Active Aerodynamic Control of a Separated Flow Using Streamwise Synthetic Jets
- 2019
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Ingår i: Flow, Turbulence and Combustion. - : Springer Science and Business Media LLC. - 1573-1987 .- 1386-6184. ; 103:4, s. 1039-1055
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Tidskriftsartikel (refereegranskat)abstract
- LES simulations at Re=1×10^5 and wind tunnel experiments at Re=5×10^5 were con-ducted to investigate the beneficial effect of an active flow control (AFC) technique on theaerodynamic performance of a simplified truck geometry. The paper involves the investiga-tion of a synthetic jet actuator characterized by periodic blowing and suction that defines azero net mass flux flow control mechanism. The actuation aims to suppress the flow sep-aration occurring at the A-pillar (front rounded corner) of a truck cabin. The work flow isdefined as it follows. First, LES at low Reynolds number are conducted for different dispo-sition of the actuation slots. The results show a beneficial effect when the actuation slots arepositioned in streamwise direction compared to spanwise (vertical) direction. Second, basedon the previous considerations, wind tunnel experiments are conducted to verify and sup-port the numerical findings. Both numerical solutions and experimental data show the sametrend and the superiority of the streamwise slots actuation when compared to traditional ver-tical slot actuation. In particular, this work shows the weakness of a vertical slot actuation,when its location is not optimized. A small change in its positioning greatly worsen the effi-cacy of the separation control in terms of drag reduction and separation bubble length. Theslot location directly affects the length of the separated flow region which its reduction canvary between 40–70% based on the positioning. Conversely, a streamwise actuation, span-ning a larger portion of the curvature of a rounded A-pillar, is not affected by this behaviourand contributes up to 80% of the recirculation bubble reduction measured in the unactuatedcase. The effect of the location change and the orientation of a zero net mass flux jet slot istherefore investigated and discussed in this work.
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| 9. |
- Chernoray, Valery, 1975, et al.
(författare)
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Flow pass a rotating cylinder with end disk: PIV measurements and RANS computations
- 2012
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Ingår i: EFMC 2012, European Fluid Mechanics Conference.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Because of the increasing attention to fuel consumption and anticipated legislation, the Flettner rotor has attained renewed interest recently as an auxiliary ship propulsion device. To improve the understanding of the flow involved, the flow structure around a Flettner rotor is studied by both three-dimensional PIV measurements and RANS simulation for a case with Re equal to 2.0 104, based on the inlet velocity (U) and cylinder diameter (D) for the aspect ratio 6, and spin ratio equal to 4.3.A test model of Flettner rotor is installed in the wind tunnel. A thin polymethyl methacrylate disk with diameter of 2D is installed at the top the cylinder following Prandtl1. The horizontal measurement plane is perpendicular to the axis of cylinder as shown in figure 1. To build up the fully three dimensional measurement data, 62 sequences of two-dimensional three components measurements at different axial position are made. The steady RANS simulation is done with SST k –ω model. The geometry of Fletter rotor as in wind tunnel measurement is used. The size of computation domain is chosen according to the one in the literature2. The domain is discretized by a hexahedral mesh, with the carefully designed boundary layer mesh around the rotor (see Figure 1). A uniform velocity inlet boundary condition is used for the inlet and slip boundary condition is chosen for the sides.Both PIV measurement and CFD show similar vortices around the rotor but with some differences as indicated in Figure 2: the simulation cannot well predict the flow at the middle plane, which important for the lift prediction. Further verification and validation will be done with force measurement.
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| 10. |
- Chernoray, Valery, 1975, et al.
(författare)
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Improving the accuracy of multihole probe measurements in velocity gradients
- 2008
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Ingår i: 2008 ASME Turbo Expo; Berlin; Germany; 9 June 2008 through 13 June 2008. - 9780791843123 ; 2, s. 125-134
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Konferensbidrag (refereegranskat)abstract
- This study describes an implementation and verification of an effective and reliable correction for the finite-size effects of pressure probes. A modified version of correction by Ligrani et al. (Exp. Fluids, vol. 7, 1989, p. 424) was used. It is shown that the correction procedure can be implemented in two steps as in Ligrani et al. or in a single step, either for probe pressures, or for velocity components. The latter correction method is found to have the best performance and studied in very detail. The effect of the correction in application to the highly three-dimensional flow downstream of the outlet guide vanes is scrutinized through detailed side-by-side comparison with corresponding cross hot-wire data. The influence of the correction on all three velocity components, flow streamlines and streamwise vorticity fields is thoroughly examined. Two flow cases with different incoming turbulence intensities are considered. The study demonstrates a very good efficiency and reliability of the correction, which lead to a significant improvement of the corrected velocity data. The improvement in crossflow velocity components has allowed correct description of the flow streamlines, and as a result, the secondary flow field structures were resolved more accurately. The considered correction does not affect the streamwise vorticity component, which is clarified as well. A very important fact is that the correction is not found to over-correct and distort the data, thus can be used safely. A very good performance of the correction for the finite-size effects of pressure probes presented in this study allows us to recommend it as a mandatory step in postprocessing procedures for multihole pressure probes.
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