Validation of PANS and active flow control for a generic truck cabin (original) (raw)

Development of Active Flowcontrol for Trucks

Proceeding of 3rd Thermal and Fluids Engineering Conference (TFEC)

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.

A Flow Control Study of a Simplified, Oscillating Truck Cabin Using PANS

Journal of Fluids Engineering

This work presents an application of the partially averaged Navier–Stokes (PANS) equations for an external vehicle flow. In particular, the flow around a generic truck cabin is simulated. The PANS method is first validated against experiments and resolved large eddy simulation (LES) on two static cases. As a consequence, PANS is used to study the effect of an active flow control (AFC) on a dynamic oscillating configuration. The oscillation of the model represents a more realistic ground vehicle flow, where gusts (of different natures) define the unsteadiness of the incoming flow. In the numerical study, the model is forced to oscillate with a yaw angle 10 deg > β > –10 deg and a nondimensional frequency St = fW/Uinf = 0.1. The effect of the periodic motion of the model is compared with the quasi-static flow condition. At a later stage, the dynamic configuration is actuated by means of a synthetic jet boundary condition. Overall, the effect of the actuation is beneficial. The a...

Experimental and computational studies of active flow control on a model truck-trailer

EPJ Web of Conferences

Active flow control is probably the most challenging research area in vehicle aerodynamics. Being able to manipulate a flow field in order to achieve desired results beneficial to engineering is the only way to meet today's demands for competitive and efficient solutions in the automotive industry. The current work studies the flow control on a semi detailed model truck by using detached-eddy simulations and wind tunnel experiments aiming at reducing the aerodynamic drag. This study combines both passive and active flow control applied on the rear end of the trailer. An indigenous fluidic actuator (loudspeaker in cavity with slots) is used as a synthetic jet in the experiment. Both experiments and computations demonstrate that the active flow control works successfully and results in flow reattachment to the flaps. The numerical simulations show that the drag coefficient, , decreased by 3.9% when AFC was activated compared to the baseline case without flaps. The corresponding decrease when AFC was deactivated (with flaps) was only 0.7%. The experimental results show a decrease of by 3.1% for the case with activated AFC compared to the baseline case. When AFC was deactivated the corresponding decrease in was 1.8%. A detailed flow analysis made in computations and experiments is used to explain these results.

Large Trucks Drag Reduction using Active Flow Control

Aerodynamic drag is the cause for more than two-thirds of the fuel consumption of large trucks at highway speeds. Due to functionality considerations, the aerodynamic efficiency of the aft regions of large trucks was traditionally sacrificed. This leads to massively separated flow at the lee side of truck trailers, with an associated drag penalty: roughly a third of the total aerodynamic drag. Active Flow Control (AFC), the capability to alter the flow behavior using small, unsteady, localized energy injection, can very effectively delay boundary layer separation. By attaching a compact and relatively inexpensive "add-on" AFC device to the back side of truck trailers (or by modifying it when possible) the flow separating from the truck trailer could be redirected to turn into the lee side of the truck, increasing the back pressure, thus significantly reducing drag. A comprehensive and aggressive research plan that combines actuator development, computational fluid dynamics and bench-top as well as wind tunnel testing was performed. The research uses an array of 15 newly developed suction and oscillatory blowing actuators housed inside a circular cylinder attached to the aft edges of a generic 2D truck model. Preliminary results indicate that a net drag reduction of 10% on full-scale trucks is achievable. * Corresponding author, seifert@eng.tau.ac.il, Associate Prof., Associate Fellow AIAA.

Experimental application of active flow control on a 1:8 scale, simplified truck model

HAL (Le Centre pour la Communication Scientifique Directe), 2014

The effect of active flow control combining synthetic jets and inclined flaps on the flow behind a 1:8 scale simplified truck model is experimentally studied. Aerodynamic drag and base pressure measurements show that forcing the flow within a given range of actuation frequencies allows reducing the drag. However, results also show that such drag reductions greatly depend on the underside flow velocity.

Computational Analysis of Active Flow Control to Reduce Aerodynamics Drag on a Van Model

2011

Method of active flow control can be applied to reduce aerodynamic drag of the vehicle. It provides the possibility to modify locally the flow, to remove or delay the separation position or to reduce the development of the recirculation zone at the back as well as the separated swirling structures around the vehicle. In this study, a passenger van is modeled with a modified form of Ahmed's body by changing the orientation of the flow from its original form (modified/reversed Ahmed Body). This model is equipped with suction and blowing on the rear side to comprehensively examine the pressure field modifications that occur in order to modify the near wall flow toward reducing the aerodynamics drag. The computational simulation used is k-epsilon flow turbulence model. In this configuration, the front part of body was inclined at an angle of 35 with respect to the horizontal. The geometry is placed in a 3D-rectangular numerical domain with length, width and height equal to 8l, 2l an...

Computations and Full-Scale Tests of Active Flow Control Applied on a VOLVO Truck-Trailer

Lecture Notes in Applied and Computational Mechanics, 2015

Large-eddy simulations and full-scale investigations aiming at the reduction of the aerodynamic drag and thus the fuel consumption of truck-trailers are carried out. The computational model is a relevant generic truck-trailer combination and the full-scale is a corresponding Volvo prototype vehicle. Passive and active flow control (AFC) approaches are adopted in this work and applied at the rear-end of the trailer. Flaps are mounted at an angle which induces separation and synthetic jet actuators are placed close to the corner of the rear-end and the flaps. The computations propose an optimal flap angle of 30 • to the free stream and C µ of 1%. The gained drag reduction is of order 30%. The flow is analyzed by comparing the phaseaveraged and time-averaged flow field of the unforced and the forced cases. The full-scale prototype consist of a Volvo truck-trailer. The trailer has been mounted by three flaps at the rear-sides and top-end. The actuators consist of loudspeakers in sealed cavities, connected to amplifiers which are supplied with a frequency generator controlled by LabVIEW. The full-scale test includes passive and active flow control investigations by varying the flap angle, with and without AFC, investigating different frequency and slot angle configurations. During the full-scale test the fuel flux is measured. The test show a fuel reduction of about 4% comparing two flap angles. The test of active flow control show a reduction of 5.3% compared to the corresponding unforced case. Compared with the baseline case, the passive flow control fail to reduce the total fuel consumption.

PIV Measurements Around a Generic Truck Model in Active Flow Control Experiments

2019

Trucks and buses play an important role in the global transportation figures, therefore reduction of aerodynamic drag becomes a relevant problem for road vehicles. For example, for a semi-truck moving at cruise speed, drag accounts for 60-80% of the total resistance of motion, being the largest source of power consumption. Many effective methods of drag reduction have been known from passive to active flow control. In this paper, a systematic study of a flow structure in active flow control mode around a cabin model of a semi-truck using controlled synthetic jets located at its rounded front edges (A-pillar) is carried out. Bimodal harmonic disturbances with different frequencies and amplitudes were used to control the flow. Optimization of parameters of a control signal was performed during an aerodynamic experiment in a wind tunnel by the use of an evolutionary algorithm. As a criterion of control effectiveness, weight measurements of aerodynamic drag force and energy expenditure ...

Numerical simulation of the flow around a simplified vehicle model with active flow control

International Journal of Heat and Fluid Flow, 2011

Large-eddy simulation (LES) was used to study the influence and the resulting flow mechanisms of active flow control applied to a two-dimensional vehicle geometry. The LES results were validated against existing Particle Image Velocimetry (PIV) and force measurement data. This was followed by an exploration of the influence of flow actuation on the near-wake flow and resulting aerodynamic forces. Not only was good agreement found with the previous experimental study, but new knowledge was gained in the form of a complex interaction of the actuation with the coherent flow structures. The resulting time-averaged flow shows a strong influence of the extension of the actuation slots and the lateral solid walls on the near-wake flow structures and thereby on the resulting drag.

Aerodynamic flow control for a generic truck cabin using synthetic jets

Journal of Wind Engineering and Industrial Aerodynamics, 2017

LES simulations at Re = 1 × 10 5 and wind tunnel experiments at Re = 5 × 10 5 were conducted to investigate the beneficial effect of an active flow control (AFC) technique on the aerodynamic performance of a simplified truck geometry. The paper involves the investigation of a synthetic jet actuator characterized by periodic blowing and suction that defines a zero net mass flux flow control mechanism. The actuation aims to suppress the flow separation occurring at the A-pillar (front rounded corner) of a truck cabin. The work flow is defined as it follows. First, LES at low Reynolds number are conducted for different disposition of the actuation slots. The results show a beneficial effect when the actuation slots are positioned in streamwise direction compared to spanwise (vertical) direction. Second, based on the previous considerations, wind tunnel experiments are conducted to verify and support the numerical findings. Both numerical solutions and experimental data show the same trend and the superiority of the streamwise slots actuation when compared to traditional vertical 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 efficacy of the separation control in terms of drag reduction and separation bubble length. The slot location directly affects the length of the separated flow region which its reduction can vary between 40-70% based on the positioning. Conversely, a streamwise actuation, spanning a larger portion of the curvature of a rounded A-pillar, is not affected by this behaviour and contributes up to 80% of the recirculation bubble reduction measured in the unactuated case. The effect of the location change and the orientation of a zero net mass flux jet slot is therefore investigated and discussed in this work.