Unsteady Aerodynamic Response of a Vehicle by Natural Wind Generator of a Full-Scale Wind Tunnel

Yamashita, Taro; Makihara, Takafumi; Maeda, Kazuhiro; Tadakuma, Kenji

doi:10.4271/2017-01-1549

Cited by 15 publications

(4 citation statements)

References 12 publications

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“…However, at higher flow rates, the smoothened response of the commercial sensor is found to be sufficient to monitor the applied pressure. Assuming laminar flow and incompressibility, the input flow velocity U is related to the applied differential pressure P as 1 2 C D ρU 2 where C D = 1.051 is the drag coefficient of a flat plate at an angle of 80 • [43] and ρ is the density of air at 25 • C. For flow rates U > 6 m s −1 , figure 6(b) indicates that the averaged reference pressures are in good agreement with the flow rates measured by the manometer. These pressure values serve as references against which the piezoelectric sensor is calibrated.…”

Section: Resultsmentioning

confidence: 99%

“…In the field of experimental aerodynamics, differential pressure sensors that can simultaneously exhibit high temporal and spatial resolution are required [1]. Automotive aerodynamic measurements typically require surface pressure sensors capable of static differential pressure measurements from −2 to 2 kPa with a response time of less than 10 ms [2].…”

Section: Introductionmentioning

confidence: 99%

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Differential pressure sensor using flexible piezoelectrics with pyroelectric compensation

Ramanathan¹,

Headings²,

Dapino³

2021

Smart Mater. Struct.

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Polyvinylidene fluoride (PVDF) is a mechanically tough, low density piezoelectric polymer commercially available as a flexible film that can be conformed to arbitrarily-shaped surfaces using simple adhesive bonding. A fundamental challenge that prevents the implementation of piezoelectric sensors for pressure sensing applications is their inability to measure static or very low frequency signals. Further, due to their large pyroelectric constants, they are limited to measurements where the rate of change in temperature is smaller than the lower cutoff frequency of the system. Under steady flow conditions, the cantilever unimorph possesses the highest sensitivity compared to other conventional configurations such as compression, doubly clamped unimorphs, or diaphragms. However, to preserve the overall noninvasive nature and linearity of the sensor, it is necessary to optimize the geometry and material properties in order to maximize charge output while minimizing deflection. To address these challenges, this work focuses on the development of a cantilever PVDF unimorph for static differential pressure measurement with pyroelectric compensation. A design optimization procedure to maximize the charge sensitivity of a cantilever unimorph is presented and the optimized cantilever is interfaced with a large-time-constant, drift-compensated charge amplifier for near-static pressure measurements. Voltage error due to temperature changes accompanying the input flow is compensated using a compressive mode sensor and an empirical compensation algorithm. Within the investigated range, the sensitivity of the fabricated sensor is 1.05 mV Pa−1 with an average resolution of 10 Pa and 97.3% linearity.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Differential pressure sensor using flexible piezoelectrics with pyroelectric compensation

Ramanathan¹,

Headings²,

Dapino³

2021

Smart Mater. Struct.

View full text Add to dashboard Cite

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“…After the results of these studies, unsteady aerodynamic forces have been recognized as important characteristics that control the motion of a vehicle. Therefore, some many researches have analyzed the effects of unsteady aerodynamic forces caused by wind flow fluctuation; the unsteady aerodynamic response measurement in wind gust (Kobayashi et al, 1988;Cogotti, 1999), the numerical analysis in wind gust (Nakashima et al, 2010), and the aerodynamic response in the simulated natural wind (Schroeck et al, 2011;Yamashita et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Investigations of unsteady aerodynamic effects generated by heave and pitch motion in different vehicle body shapes with model excitation tests

Maeda

Tsubakino

Hara

et al. 2020

Mechanical Engineering Journal

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In this study, unsteady aerodynamic forces induced by forced pitch and heave motions are measured and formulated to the unsteady aerodynamic coefficients by utilizing the 1/4-scale nearly actual vehicle model with wheels and wheel-houses and a system without unnecessary stings exposed to the flow. The unsteady aerodynamic lift forces are measured as input forces at front and rear axles in vehicle suspensions for each, and are expressed as the aerodynamic inerter, aerodynamic damping and aerodynamic spring coefficients which are equivalent in vehicle suspension property. These studies are conducted with less than 1.4 × 10 6 of Reynolds number and with less than 0.2 of non-dimensional frequency. From the results, it is observed the effect of front aerodynamic forces in proportion to motion acceleration which works as an inerter can be ignored in both of pitch and heave motion, but the effect of rear aerodynamic forces as an inerter must be considered in both motion, and the first-order lag must be considered additionally about the rear only in heave motion. Furthermore, the large difference of unsteady aerodynamic characteristics is obtained while comparing in different vehicle body shapes which are without and with a protrusion on the roof. Especially, the difference of unsteady aerodynamic forces of rear in pitch motion is much large. In the case without the protrusion, the aerodynamic inerter which restrains pitch motion is occurred. On the other hand, in the case with the protrusion, the effect of aerodynamic inerter decreases and other aerodynamic forces promotes pitch motion in opposite. The phenomenon of this difference is closely related to the behavior of flow velocities at near surface around the model. From the above, it is confirmed that the large difference of unsteady aerodynamic forces induced by motions occurs in the detail difference of body shapes at a nearly actual vehicle model, and can be expressed quantitatively as the difference of aerodynamic response.

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“…In order to simulate turbulence and fluctuating yaw angles, several automobile full-scale and model scale wind tunnels have added systems to create transient incident flow. Among these are the Pininfarina wind tunnel [7,8] and more recently Durham University's model scale tunnel [9] as well as Toyota's new full-scale tunnel [10].…”

Section: Introductionmentioning

confidence: 99%

The Influence of Different Unsteady Incident Flow Environments on Drag Measurements in an Open Jet Wind Tunnel

Xiao

Jessing

Kuthada

et al. 2020

Fluids

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Aerodynamic development for road vehicles is usually carried out in a uniform steady-state flow environment, either in the wind tunnel or in Computational Fluid Dynamics (CFD) simulations. However, out on the road, the vehicle experiences unsteady flow with fluctuating angles of incidence β, caused by natural wind, roadside obstacles, or traffic. In order to simulate such flow fields, the Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (FKFS) swing® system installed in the quarter scale model wind tunnel can create a variety of time-resolved signals with variable β. The static pressure gradient in the empty test section, as well as cD values of the Society of Automotive Engineers (SAE) body and the DrivAer model, have been measured under these transient conditions. The cD measurements have been corrected using the Two-Measurement Correction method in order to decouple the influence of the unsteady flow from that of the static pressure gradient. The investigation has determined that the static pressure gradient in the empty test section varies greatly with different excitation signals. Thus, it is imperative to apply a cD correction for unsteady wind tunnel measurements. The corrected cD values show that a higher signal amplitude, as in, signals with large β, lead to higher drag forces. The influence of the signal frequency on drag values varies depending on the vehicle geometry and needs to be investigated further in the future.

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Unsteady Aerodynamic Response of a Vehicle by Natural Wind Generator of a Full-Scale Wind Tunnel

Cited by 15 publications

References 12 publications

Differential pressure sensor using flexible piezoelectrics with pyroelectric compensation

Differential pressure sensor using flexible piezoelectrics with pyroelectric compensation

Investigations of unsteady aerodynamic effects generated by heave and pitch motion in different vehicle body shapes with model excitation tests

The Influence of Different Unsteady Incident Flow Environments on Drag Measurements in an Open Jet Wind Tunnel

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