| 1. |
- Abbafati, Cristiana, et al.
(författare)
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- 2020
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Habibi, Maryam, et al.
(författare)
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Corrosion resistance and surface microstructure of Mg 3 N 2 / SS thin films by plasma focus instrument
- 2022
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Ingår i: Microscopy research and technique (Print). - : Wiley. - 1059-910X .- 1097-0029. ; 85:8, s. 2880-2893
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing a plasma focus (PF) instrument, magnesium nitride (Mg3 N2 ) thin films were synthesized on stainless steel substrates. Twenty five optimum focus shots at 8 cm distance from the anode tip were used to deposit the films at different angular positions regarded to the anode axis. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses were performed to assess the surface morphology and structural characteristics of Mg3 N2 films. Based on AFM images, these films were studied to understand the effect of angular position variation on their surfaces through morphological and fractal parameters. By increasing the angle, we verify that the grain size decreased from 130(0) nm to 75(5) nm and also the mean quadratic surface roughness of the films reduced in its average values from (28.97 ± 3.24) nm to (23.10 ± 1.34) nm. Power spectrum density analysis indicated that films become more self-affine at larger angles. Furthermore, the corrosion behavior of the films was investigated through a potentiodynamic polarization test in H2 SO4 solution. It was found that the ion energy and flux, varying with the angular positions from the anode tip, directly affected the nanostructured roughness and surface morphology of the samples. The electrochemical studies of films show that the uncoated sample presented the lowest corrosion resistance. The highest corrosion resistance was obtained for the sample deposited with 25 optimum shots and at 0° angular position reaching a reduction in the corrosion current density of almost 800 times compared to the pure stainless steel-304 substrate.
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| 3. |
- Köroglu, Hakan, 1971, et al.
(författare)
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Platoon Control under a Novel Leader and Predecessor Following Scheme with the Use of an Advanced Aerodynamic Model
- 2018
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Ingår i: Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME. - : ASME International. - 0022-0434 .- 1528-9028. ; 140:4
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Tidskriftsartikel (refereegranskat)abstract
- The longitudinal platoon control problem is considered under a leader and predecessor following scheme with a novel velocity-dependent spacing policy. With this spacing policy, the steady-state inter-vehicle distances increase with increasing cruise velocity and more so for vehicles that are closer to the leader.} Since significant changes might be encountered in inter-vehicle distances during the travel due to the variations in the velocity of the leader, the problem is studied together with a more accurate modeling of aerodynamic effects within a platoon formation. Based on a standard feedback linearization approach, a dynamic output feedback synthesis problem is formulated with two H_infinity performance objectives. One of the performance objectives is linked to the string stability of the platoon formation, while the other can be shaped in a way to maintain small spacing errors without aggressive vehicle maneuvers. A synthesis procedure is then outlined based on linear matrix inequality optimization. The new control scheme is investigated for a three-vehicle platoon by using an advanced aerodynamic model developed based on extensive fluid dynamics simulations. It is observed in this investigation that a desirable platoon operation can be achieved even with a simple aerodynamic model, provided that the controller is designed in a way to ensure good disturbance attenuation. Nevertheless an accurate modeling of aerodynamic disturbances might be needed especially for the first vehicle after the leader when the cruising velocity varies over a wide range.
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| 4. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Large Eddy Simulation of the flow and heat transfer in a half-corrugated channel with various wave amplitudes
- 2014
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 76, s. 432-446
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Tidskriftsartikel (refereegranskat)abstract
- Large Eddy Simulation (LES) of turbulent flow and convective heattransfer over a half-corrugated channel is presented in this paper. Simulationsare performed for various ranges of the normalized wave amplitudes,AM = 0 − 0.15 (the ratio of wave height to wave length). The Reynoldsnumber based on the bulk velocity is chosen as Reb = 10 000 and thePrandtl number is Pr=0.71. A comparison between the DNS and LESresults of a plane channel (AM = 0) at Re = 395 is also performed.The obtained results indicate that the region of recirculating flow dependsstrongly on the wave amplitude. This study shows that the Nusseltnumber (Nu) increases by increasing the wave amplitude until a specificvalue then it remains approximately constant. The thermal performanceparameter (JF) is used as a measure for the heat transfer enhancementrelative to the pressure drop and it is found that the maximum values ofNu and JF appear at AM = 0.1, which hence correspond to the optimumvalue of the wave amplitude.
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| 5. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Large Eddy Simulations of Flow Around Two Generic Vehicles in a Platoon
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783319306025 ; 185, s. 283-288
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Konferensbidrag (refereegranskat)abstract
- A detailed analysis of the effect of inter-vehicle distance on the flow structure of a two-model platoon is presented. Simulations are made for two Ahmed bodies with a slant angle of 25 degrees and for three inter-vehicle distances, d/L = 0.3, 0.5 and 1. The Reynolds number based on the body height was 30000. A drag increase was observed for the follower with d/L = 0.5, compared to the drag value of a single body in isolation. To explain the underlying reasons for the increase in drag, various instantaneous and time-averaged plots are presented and compared for different distances, and a significant change in flow structure was found in flows between the set-ups with d/L = 0.5 and d/L = 1.
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| 6. |
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| 7. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Numerical Study of Aerodynamic Interactions in a Homogeneous Multi-vehicle Formation
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783319306025 ; 185, s. 289-294
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Konferensbidrag (refereegranskat)abstract
- An accurate and affordable method to study the flow features associated with vehicles in a homogeneous platooning is presented in this paper. It was found that only one pitch of a long-line periodic platoon would provide a sufficiently accurate observation of the flow interaction in the inter-vehicle region of the vehicles offering a significant reduction of the computational effort. The simulations of flow at Reynolds number of 30000 are made for a periodic platoon including slanted-back Ahmed bodies with a slant angle of 25 degrees and for four inter-vehicle distances, d/L = 0.1, 0.3, 0.5 and 1.
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| 8. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Partially-Averaged navier-stokes simulations of flows around two different ahmed bodies
- 2015
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Ingår i: Computers and Fluids. - : Elsevier BV. - 0045-7930. ; 117, s. 273-286
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Tidskriftsartikel (refereegranskat)abstract
- The paper reports a study about the prediction of flows around simplified vehicles using Partially-Averaged Navier-Stokes (PANS). Numerical simulations are performed for two simplified vehicles: a slanted-back Ahmed body at Re. =. 30,000 and a squared-back Ahmed body at Re. =. 300,000. A comparison of the resolved and modeled physical flow scales is made with corresponding LES and experimental data for a better understanding of the performance of the PANS model. The PANS model is compared for coarse and fine grid resolutions and it is indicated that even a coarse-grid PANS simulation is able to produce fairly close flow predictions to those from a well-resolved LES simulation. The results indicate the possibility of improvement of the predictions by employing a finer grid resolution.
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| 9. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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The effect of corrugation on heat transfer and pressure drop in channel flow with different Prandtl numbers
- 2013
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 66, s. 164-176
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Tidskriftsartikel (refereegranskat)abstract
- Large Eddy Simulation and Direct Numerical Simulation are applied to study the turbulent flow field in a wavy channel at two Prandtl numbers, Pr = 0.71 and Pr = 3.5, and Reynolds number Re b = 10,000. The characteristics of the separated shear layer and the near wall recirculating zone are discussed in relation to the turbulent heat transfer. Special attention is paid to the behavior of the flow and thermal boundary layers and various turbulent characteristics and their effects on the distribution of the Nusselt number and friction coefficient in the separation and reattachment regions. The results indicate that the thickness of the thermal boundary layer rather than the turbulent fluctuations has a significant effect on the local variation of the averaged Nusselt number. The results are compared with Direct Numerical Simulation results of a plane channel at the same Reynolds number. © 2013 Elsevier Ltd. All rights reserved.
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| 10. |
- Sharma, Rohini, 1990, et al.
(författare)
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FlexiGrid Tools for Real-Life Demonstrations of Local Energy System Concepts at Chalmers Campus Testbed
- 2023
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Ingår i: 2023 IEEE Belgrade PowerTech. - 9781665487788
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Konferensbidrag (refereegranskat)abstract
- The ongoing transition in the energy system is accompanied by various challenges such as congestion and voltage violations in electricity distribution networks. Suggested solutions to these challenges are, among others, local energy and flexibility markets, new tariff designs, and centralized control. Simulation and demonstration of such solutions often require a broad chain of tools that need to be automated. The aim of this paper is to present a simulation and demonstration platform integrating several of the required tool and their deployment at the Chalmers Campus test bed. The developed tools include PV and load forecasting, congestion forecasting, energy management system, model predictive control algorithms, and local energy and flexibility markets. The tools are integrated using a common and reusable platform called LESOOP for simulation and demonstration. Demonstration examples of PV and load forecasts, congestion forecasts, model predictive control, and energy management systems are presented and results are discussed. The paper contributes to a more successful transition of the energy system by sharing experiences and provides better understanding of the tool functionalities at the Chalmers campus test-bed. The identified gaps and gained knowledge from the real-life demonstrations at the test-bed can be valuable to projects and researchers aiming to develop a test-bed.
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