Browse Topic: Wind tunnel tests
Homologation is an important process in vehicle development and aerodynamics a main data contributor. The process is heavily interconnected: Production planning defines the available assemblies. Construction defines their parts and features. Sales defines the assemblies offered in different markets, where Legislation defines the rules applicable to homologation. Control engineers define the behavior of active, aerodynamically relevant components. Wind tunnels are the main test tool for the homologation, accompanied by surface-area measurement systems. Mechanics support these test operations. The prototype management provides test vehicles, while parts come from various production and prototyping sources and are stored and commissioned by logistics. Several phases of this complex process share the same context: Production timelines for assemblies and parts for each chassis-engine package define which drag coefficients or drag coefficient contributions shall be determined. Absolute and
When traveling in an open-jet wind tunnel, the path of an acoustic wave is affected by the flow causing a shift of source positions in acoustical maps of phased arrays outside the flow. The well-known approach of Amiet attempts to correct for this effect by computing travel times between microphones and map points based on the assumption that the boundary layer of the flow, the so-called shear layer, is infinitely thin and refracts the acoustical ray in a conceptually analogy to optics. However, in reality, the turbulent nature of both the not-so-thin shear layer and the acoustic emission process itself causes an additional smearing of sources in acoustic maps, which in turn causes deconvolution methods based on these maps – the most prominent example being CLEAN-SC – to produce certain ring effects, so-called halos, around sources. In this paper, we intend to cast some light on this effect by describing our path of analyzing/circumventing these halos and how they are linked to the
The mystery of how futuristic aircraft embedded engines, featuring an energy-conserving arrangement, make noise has been solved by researchers at the University of Bristol. University of Bristol, Bristol, UK A study published in Journal of Fluid Mechanics, reveals for the first time how noise is generated and propagated from these engines, technically known as boundary layer ingesting (BLI) ducted fans. BLI ducted fans are similar to the large engines found in modern airplanes but are partially embedded into the plane's main body instead of under the wings. As they ingest air from both the front and from the surface of the airframe, they don't have to work as hard to move the plane, so it burns less fuel. The research, led by Dr. Feroz Ahmed from Bristol's School of Civil, Aerospace and Design Engineering under the supervision of Professor Mahdi Azarpeyvand, utilized the University National Aeroacoustic Wind Tunnel Facility. They were able to identify distinct noise sources originating
Unsteady pressure fluctuations in launch vehicles can induce aerodynamic instabilities, potentially resulting in vibration, structural fatigue, and even catastrophic failure. These risks undermine structural integrity and jeopardize payload delivery, threatening mission success and crew safety. Therefore, precise measurements of unsteady pressure are vital for understanding dynamic pressure distribution and flow behaviour caused by phenomena like shock waves, vortices, boundary layer interactions, and flow separation. While ground-based wind tunnel tests have conventionally provided these insights, this paper presents an on-board system designed for real-time unsteady pressure data acquisition. The system addresses the challenge of accurately resolving high-frequency pressure variations over very high base pressure values. It can be integrated into re-entry vehicles and stage recovery experiments, providing confidence in acquiring data for complex geometrical shapes. Moreover, the
MSIL (Maruti Suzuki India Limited), India’s leading carmaker, has various SUVs (Sports Utility Vehicle) in its model lineup. Traditionally, SUVs are considered to have a bold on-road presence and this bold design language often deteriorates aerodynamic drag performance. Over the years, the demand for this segment has significantly grown, whereas the CAFE (Corporate Average Fuel Economy) norms have become more stringent. To cater this growing market demand, MSIL planned for two new SUVs: (1) New BREZZA - A bolder design with similar targeted aerodynamic performance compared to its predecessor (BREZZA-2016) and (2) FRONX - A new cross-over SUV vehicle targeted best-in-class aerodynamic performance in this category at MSIL. This paper illustrates the aerodynamic development process for these two SUVs using CFD (Computational Fluid Dynamics) and full scale WTT (Wind Tunnel Test). During the initial stages, the bolder design of the New BREZZA (2022) deteriorated the aerodynamic drag of the
Meeting customer expectations along with regulatory requirements for efficiency and emissions reduction requires that even highly functional automotive products, such as 4x4s, are developed for aerodynamics efficiency. This is true of iconic vehicles, such as the Land Rover Defender. This paper discusses the redefinition of an icon: the aerodynamics development of the All-New Land Rover Defender. It outlines a strategy based on integrating simulation and test approaches: unsteady Computational Fluid Dynamics (CFD) simulation and Full-Scale Wind Tunnel testing. After outlining the integrated development model built around these toolsets, it demonstrates the natural fit between early phase work and simulation, where the focus was on optimizing vehicle volumes and proportions. The growing use of wind tunnel testing, as the design matures, is also explored, starting with full scale clay models before transitioning to a more representative bespoke test property. The overall development
During the pure electric vehicle high speed cruise driving condition, the unsteady air flow in the chassis cavity is susceptible to self-sustaining oscillations phenomenon. And the aerodynamic oscillation excitation could be coupled with the cabin interior acoustic mode through the body pressure relief vent, the low frequency booming noise may occur and seriously reduces the driving comfort. This paper systematically introduces the characteristics identification and the troubleshooting process of the low frequency aerodynamic noise case. Firstly, combined with the characteristics of the subjective jury evaluation and objective measurement, the acoustic wind tunnel test restores the cabin booming phenomenon. The specific test procedure is proposed to separate the noise excitation source. Secondly, according to the road test results, it is inferenced that the formation mechanism of low frequency noise is the self- sustaining oscillation with the underbody shedding vortex feedback
Planning for charging in transport missions is vital when commercial long-haul vehicles are to be electrified. In this planning, accurate range prediction is essential so the trucks reach their destinations as planned. The rolling resistance significantly influences truck energy consumption, often considered a simple constant or a function of vehicle speed only. This is, however, a gross simplification, especially as the tire temperature has a significant impact. At 80 km/h, a cold tire can have three times higher rolling resistance than a warm tire. A temperature-dependent rolling resistance model is proposed. The model is based on thermal networks for the temperature at four places around the tire. The model is tuned and validated using rolling resistance, tire shoulder, and tire apex temperature measurements with a truck in a climate wind tunnel with ambient temperatures ranging from -30 to 25 °C at an 80 km/h constant speed. Dynamic tire simulations were conducted using a heat
This paper contributes to the Committee on Commonized Aerodynamics Automotive Testing Standards (CAATS) initiative, established by the late Gary Elfstrom. It is collaboratively compiled by automotive wind tunnel users and operators within the Subsonic Aerodynamic Testing Association (SATA). Its specific focus lies in automotive wind tunnel test techniques, encompassing both those relevant to passenger car and race car development. It is part of the comprehensive CAATS series, which addresses not only test techniques but also wind tunnel calibration, uncertainty analysis, and wind tunnel correction methods. The core objective of this paper is to furnish comprehensive guidelines for wind tunnel testing and associated techniques. It begins by elucidating the initial wind tunnel setup and vehicle arrangement within it. Subsequently, it delves into a diverse array of test techniques, encompassing aerodynamic force measurements, ventilation drag assessments, flow field analyses, and surface
This ARP describes methods that are known to have been used by aircraft manufacturers to evaluate aircraft aerodynamic performance and handling effects following application of aircraft ground deicing/anti-icing fluids (“fluids”), as well as methods under development. Guidance and insight based upon those experiences are provided, including: Similarity analyses. Icing wind tunnel tests. Flight tests. CFD and other numerical analyses. This ARP also describes: The history of evaluation of the aerodynamic effects of fluids. The effects of fluids on aircraft aerodynamics. The testing for aerodynamic acceptability of fluids for SAE and regulatory qualification performed in accordance with AS5900. Additionally, Appendices A to E present individual aircraft manufacturers’ histories and methodologies, which substantially contributed to the improvement of knowledge and processes for the evaluation of fluid aerodynamic effects, and Appendix F considers the modeling of fluid removal from
Knowing the tire pressure during driving is essential since it affects multiple tire properties such as rolling resistance, uneven wear, and how prone the tire is to tire bursts. Tire temperature and cavity pressure are closely tied to each other; a change in tire temperature will cause an alteration in tire cavity pressure. This article gives insights into which tire temperature measurement position is representative enough to estimate pressure changes inside the tire, and whether the pressure changes can be assumed to be nearly isochoric. Climate wind tunnel and road measurements were conducted where tire pressure and temperature at the tire inner liner, the tire shoulder, and the tread surface were monitored. The measurements show that tires do not have a uniform temperature distribution. The ideal gas law is used to estimate the tire pressure from the measured temperatures. The results indicate that of the compared temperature points, the inner liner temperature is the most
With increasing interest in the urban air traffic market for electric Vertical Take-Off and Landing (eVTOL) vehicles, there are opportunities to enhance flight performance through new technologies and control methods. One such concept is the propulsion wing, which incorporates a cross-flow fan (CFF) at the wing's trailing edge to drive the vehicle's flight. This article presents a wind tunnel experiment aimed at analyzing the aerodynamic characteristics of the propulsive wing for the novel eVTOL vehicle. The experiment encompasses variations in angels of attack, free stream velocities and fan rotational speeds. The result verifies that cross-flow fans offer unique flow control capabilities, achieving a tested maximum lift coefficient exceeding 7.6. Since flow from the suction surface is ingested into the CFF, the flow separation at large angle of attack (up to 40°) is effectively eliminated. The aerodynamic performance of the propulsive wing depends on the advance ratio and angle of
Ice prediction capabilities for Unmanned Aerial Systems (UAS) is of growing interest as UAS designs and applications become more diverse. This report summarizes the current state-of-the-art in modeling aircraft icing within a computational framework as well as a recent U.S. Army DEVCOM AvMC effort to evaluate ice prediction models for current use and future integration into the Computational Research and Engineering Acquisition Tools and Environments (CREATE) Air Vehicle (AV) framework. U.S. Army Combat Capabilities Development Command, Redstone Arsenal, Alabama Historically, smaller Unmanned Aerial Systems (UAS), such as Class 2 RQ-1B Raven and Class 3 RQ-7Bv2 Shadow, have been restricted to not be approved to fly in icing conditions under the assumption that any ice accretion would cause an unacceptable risk of loss of the aircraft. However, interest exists in better understanding potential icing accretion on UAS to determine if less extreme icing conditions could result in only
Historically, smaller Unmanned Aerial Systems (UAS), such as Class 2 RQ-1B Raven and Class 3 RQ-7Bv2 Shadow, have been restricted to not be approved to fly in icing conditions under the assumption that any ice accretion would cause an unacceptable risk of loss of the aircraft. However, interest exists in better understanding potential icing accretion on UAS to determine if less extreme icing conditions could result in only partial degradation and not total loss of the vehicle for the purpose of expanding approved flight envelopes. Icing accretion can be tested during a flight test, which is considered unacceptable due to lack of controlled conditions and risk to the UAS or in a controlled experiment, by using wind tunnel testing to evaluate a single icing condition. Cryogenic wind tunnel tests, such as those conducted at the National Aeronautical and Space Administration (NASA) Glenn Icing Research Tunnel (IRT), Cleveland, OH, as shown in figures 1 and 2, are prohibitively expensive
Many important physical problems in aero-sciences involve unsteady, separated flows. The ability to measure and compute these flows has been a persistent challenge. Unsteady aerodynamics leads to unsteady loads which ultimately decrease system performance and shortens the system lifetime. Currently, dynamic pressure transducers are used to study unsteady flow in wind tunnel tests, which are expensive and do not provide accurate integrated unsteady loads on a wind tunnel model
Super-cooled large drops present serious threats to aviation safety and as a result, the problem has been addressed by the FAA with the additional icing certification requirement. SLD clouds often consist of bi-modal drop size spectra leading to great challenges when it comes to simulating and characterizing these conditions in situ and in icing wind tunnels. Legacy instrumentation for measuring drop size distributions and liquid water content has been challenged under these conditions. In this report, a high-resolution particle imaging instrument is described; this instrument addresses the need for measuring drop size distributions and liquid water content over a wide range of drop sizes (10 to 2500 μm or larger). A high-throughput megapixel digital camera is used to record shadow images of the particles. High-quality illumination of the particle field is provided with high-power LED illumination with driving electronics designed to provide pulse durations as short as 25ns with
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