Estimation of bluff body transient aerodynamic loads using an oscillating model rig

A method for the estimation of transient aerodynamic data from dynamic wind tunnel tests has been developed and employed in the study of the unsteady response of simple automotive type bodies. The experimental setup consists of the test model mounted to the oscillating model facility such that it is constrained to oscillate with a single degree of freedom of pure yawing motion. The yaw position is recorded from a potentiometer and the time response provides the primary measurement. Analysis of the wind-off and wind-on response allows the transient aerodynamic loads to be estimated. The frequency of oscillation, (synonymous with the frequency of disturbing wind input) is modified by altering the mechanical stiffness of the facility. The effects of Reynolds number and oscillation frequency are considered and the model is shown to exhibit damped, self-sustained and self-excited behaviour. The transient results are compared with a quasi-steady prediction based on conventional tunnel balance data and presented in the form of aerodynamic magnification factor. The facility and analysis techniques employed are presented and the results of a parametric study of model rear slant angle and of the influence of C-pillar strakes is reported. The results are strongly dependent on shape but for almost all rear slant angles tested the results show that the transient response exceeds that predicted from steady state data. The level of unsteadiness is also significantly influenced by the rear slant angles. The addition of C-pillar strakes is shown to stabilise the flow with even small strakes yielding responses below that of steady state. From the simulation results the self-sustained oscillation is shown to occur when the aerodynamic damping cancels the mechanical damping. The unsteadiness in the oscillation can be simulated by adding band-limited white noise with an intensity close to that of the turbulence intensity found in the wake. From vehicle crosswind simulation results the aerodynamic yaw moment derivative and its magnification factor are shown to be the important parameters influencing the crosswind sensitivity and path deviation

Estimation of bluff body transient aerodynamic loads using an oscillating model rig

A method for the estimation of transient aerodynamic data from dynamic wind tunnel tests has been developed and employed in the study of the unsteady response of simple automotive type bodies. The experimental setup consists of the test model mounted to the oscillating model facility such that it is constrained to oscillate with a single degree of freedom of pure yawing motion. The yaw position is recorded from a potentiometer and the time response provides the primary measurement. Analysis of the wind-off and wind-on response allows the transient aerodynamic loads to be estimated. The frequency of oscillation, (synonymous with the frequency of disturbing wind input) is modified by altering the mechanical stiffness of the facility. The effects of Reynolds number and oscillation frequency are considered and the model is shown to exhibit damped, self-sustained and self-excited behaviour. The transient results are compared with a quasi-steady prediction based on conventional tunnel balance data and presented in the form of aerodynamic magnification factor. The facility and analysis techniques employed are presented and the results of a parametric study of model rear slant angle and of the influence of C-pillar strakes is reported. The results are strongly dependent on shape but for almost all rear slant angles tested the results show that the transient response exceeds that predicted from steady state data. The level of unsteadiness is also significantly influenced by the rear slant angles. The addition of C-pillar strakes is shown to stabilise the flow with even small strakes yielding responses below that of steady state. From the simulation results the self-sustained oscillation is shown to occur when the aerodynamic damping cancels the mechanical damping. The unsteadiness in the oscillation can be simulated by adding band-limited white noise with an intensity close to that of the turbulence intensity found in the wake. From vehicle crosswind simulation results the aerodynamic yaw moment derivative and its magnification factor are shown to be the important parameters influencing the crosswind sensitivity and path deviation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The measurement of transient aerodynamics using an oscillating model facility

A method for the estimation of transient aerodynamic data from dynamic wind tunnel tests has been developed and employed in the study of the unsteady response of simple automotive type bodies. The paper describes the facility and analysis techniques employed and reports the results of a parametric study of model rear slant angle and of the influence of C-pillar strakes. The model is shown to exhibit damped, self-sustained and self-excited behaviour. The transient results are compared with quasi-steady predictions based on conventional tunnel balance data through the calculation of derivative magnification factors. For all slant angles tested the results show that the quasi-steady prediction is a poor estimate of the real transient behaviour. In addition the slant angle is shown to have significant effect on the level of unsteadiness. The addition of Cpillar strakes is shown to stabilise the flow with even small height strakes yielding responses well below that of steady-state

Estimation of bluff body transient aerodynamics using an oscillating model rig

A method for the estimation of transient aerodynamic derivatives from dynamic wind tunnel tests using time response data is presented in this paper. For the purposes of the study, the aerodynamic derivatives are considered to act as a stiffness and damping to the model motion. The experimental set-up consists of a simple bluff body (Davis model) constrained to oscillate with a single degree of freedom of pure yawing motion. A range of springs were used to control the oscillation frequency and hence the reduced frequency. The transient responses from dynamic wind tunnel tests are compared with quasi-steady analysis in order to investigate the effect of unsteady aerodynamics. The aerodynamic derivatives are initially estimated using the classical logarithmic decay method. The dynamic stiffness derivative exceeds that determined statically across the reduced frequency range. The damping derivative was found to be a function of free-stream speed; at low velocities it is negative but progressively increases to a positive value. With further increases in speed, a self-sustained oscillation is observed with almost constant frequency and amplitude. This result is attributed to coupling between the model wake and the model stability; however, the exact mechanism of the interaction is not fully understood. This phenomenon is under further investigation

Impact of adjacent building on outdoor ventilation around a layout of two buildings

The outdoor air ventilation impact ofa taller building in different configurations of a layout of two adjacent buildings is presented in this paper. The critical parameters investigated are the separation distance (S) between the buildings and the ratio of height of downwind building to that of the building upwind, herein referred to as building height ratio (HR). The aim is to explore intermediate spacing distances which may engender acceptable ventilation around the buildings.A three-dimensional (3-D) numerical simulation employing the Computational Fluid Dynamics technique which adopts the Reynolds-Averaged Navier-Stokes equation and the realizable k-e turbulence model was used to study the turbulent flow field around the full-scale two-building configurations.Results show that velocity ratio generally increases with height ratio, indicating that more air motion is induced at the pedestrian level as the height of the downwind building increases. For each of the height ratios, there is a spacing distance at which the velocity ratio is highest. The spacing distances at which the maximum velocity ratio occurs for the various height ratios are proposed. The dimensionless air exchange rate generally increases with height ratio, indicating that greater quantity of air from within the cavity between the buildings is exchanged with air from outside the cavity, which should result in better air quality. The findings of the study demonstrate the importance of incorporating wind data of an urban area in formulating guidelines for layout of buildings in the area

Yaw Angle Effect On The Aerodynamic Performance Of Hatchback Vehicle Fitted With Wing Spoiler

Research on spoiler available to date was mainly done to optimize the performance of spoiler in non-zero yaw condition. However, the effect of spoiler is most needed during cornering to ensure the stability of the vehicle. Therefore, this study aims to inspect the effect of yaw angles change on the aerodynamic performance of the NACA 0018 wing spoiler and the subsequent influence on the flow characteristics of the hatchback vehicle. Computational Fluid Dynamics (CFD) has been applied to model the flow. Comparison between numerically obtained results and experimental data was done to validate the CFD method. The findings show that both the drag coefficient, Cd, and lift coefficient, Cl have increased with increasing yaw angle. However, the spoiler has performed in favor of reducing the Cd and Cl even with increasing yaw angle. The averaged proportion contributions from the spoiler to the overall Cd and Cl are 2.7% and 4.1%, respectively. The other body parts that have contributed to the Cd and Cl reductions were the base and slant, and the roof

Yaw angle effect on the aerodynamic performance of hatchback vehicle fitted with wing spoiler

Research on spoiler available to date was mainly done to optimize the performance of spoiler in non-zero yaw condition. However, the effect of spoiler is most needed during cornering to ensure the stability of the vehicle. Therefore, this study aims to inspect the effect of yaw angles change on the aerodynamic performance of the NACA 0018 wing spoiler and the subsequent influence on the flow characteristics of the hatchback vehicle. Computational Fluid Dynamics (CFD) has been applied to model the flow. Comparison between numerically obtained results and experimental data was done to validate the CFD method. The findings show that both the drag coefficient, Cd, and lift coefficient, Cl have increased with increasing yaw angle. However, the spoiler has performed in favor of reducing the Cd and Cl even with increasing yaw angle. The averaged proportion contributions from the spoiler to the overall Cd and Cl are 2.7% and 4.1%, respectively. The other body parts that have contributed to the Cd and Cl reductions were the base and slant, and the roof

Experimental and simulation Studies of a Two Seater Light Aircraft

This paper presents the aerodynamic studies carried out on a three-dimensional aircraft model. The test model is a 15% scaled down from a two-seater light aircraft that close to the Malaysian made SME MD3-160 aircraft. The aircraft model is equipped with control surfaces such as flaps, aileron, rudder and elevator and it is designed for pressure measurement testing and direct force measurement using a 6-components balance system. This aircraft model has been tested at two different low speed tunnels, at Universiti Teknologi Malaysia tunnel sized 1.5 x 2.0 meter2 test section, and at Institute Aerodynamic Research, National Research Council of Canada sized 3 x 2 meter2 tunnel. The speed during testing at UTM and IAR/NRC tunnels was up to 70 meter/second, which is corresponds to Reynolds numbers of 1.3 x 106.The longitudinal and lateral directional aerodynamic characteristics of the aircraft such as coefficients of pressure, forces (lift, drag, side) and moments (roll, pitch and yaw) have been experimentally measured either using direct force measurement or pressure measurement method. The data reduction methods include the strut support interference factor using dummy image and the blockage correction have been applied in this project. The results showed that for the undeployed flap configuration, the stalling angle of this aircraft is 160 at CLMax = 1.05 measured by UTM - LST, compared to CLMax =1.09 at stalling angle 150 by IAR- NRC. Beside the experimental study, simulation also be performed by using a commercial Computational Fluid Dynamics (CFD) code, FLUENT Version 5.3. Experimental works at UTM and IAR – NRC tunnel show that the aerodynamic characteristics of this light aircraft are in a good agreement with each other. Simultaneously, the aerodynamic forces obtained from experimental works and CFD simulations have been compared. The results proved that they are agreeable especially at a low angle of attack

Sustainable Design & Product and Health & Safety Awareness among Public University Students

In this article, the focus is on understanding the awareness of sustainable design & product and health & safety among engineering and architectural students at university levels as these young graduates are representative of the workforce. This survey was conducted at five public universities in Peninsular Malaysia. On average, the majority of respondents provided positive responses (more than 80%) on the needs of sustainable design & product and health & safety aspects in their workplaces. These figures bode well for such an ambitious country to be on par with developed countries. It is also noteworthy to highlight that a significant portion who are not comfortable with investing with sustainable features.  Keywords: Sustainable Design & Products; Health and Safety (H&S) eISSN: 2398-4287© 2020. The Authors. Published for AMER ABRA cE-Bsby e-International Publishing House, Ltd., UK. This is an open access article under the CC BYNC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. DOI: https://doi.org/10.21834/ebpj.v5iSI3.257

Validation of CFD modeling and simulation of a simplified automotive model

In the early design phase of automotive sector, the flow field around the vehicle is important in decision making on design changes. It would consume a lot of money and time for multiple prototypes development if adopt traditional testing method which is wind tunnel test. Thus, numerical method such as Computational Fluid Dynamics (CFD) simulation plays an important role here. It is very often simulation results been compared with wind tunnel data. However, with various mesh types, meshing methodology, discretization methods and different solver control options in CFD simulation, users may feel low confidence level with the generated simulation results. Thus, a robust modeling and simulation guideline which would help in accurate prediction should be developed due to the industry’s demand for accuracy when comparing CFD to wind tunnel results within short turnaround time. In this paper, a CFD modeling and simulation study was conducted on a simplified automotive model to validate with wind tunnel test results. The wind tunnel environment was reproduced in the simulation setup to include same boundary conditions. Meshing guidelines, turbulence model comparisons and also the best practice for solver setup with respect to accuracy will be presented. Overall, CFD modeling and simulation methods applied in this paper are able to validate the results from experiment accurately within small yaw range