| 1. |
- 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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| 2. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Experimental and numerical study of flow structures between two Ahmed bodies with various inter-body distances
- 2015
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Ingår i: Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer. - 2377-2816. ; 0, s. 835-838
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Konferensbidrag (refereegranskat)abstract
- Numerical and experimental study of mutual interaction of flow structures in a two-vehicle platoon is presented in this paper. The investigations were conducted for the vehicles distances in the range of d/L = 0-1.3 at Re = 130, 000. The experimental observations showed a sudden unexpected drag increase of the follower at specific close distances of the bodies in which, the velocity fluctuations of the shear layer separated from the leader suddenly increases. Accurate PANS numerical simulations were performed at three alternative close distances of the bodise which increased understanding of the flow structures.
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| 3. |
- 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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| 4. |
- 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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| 5. |
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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