Virtual Wind Tunnel Research Articles

Modelling a virtual wind tunnel for vehicle aerodynamic measurements

The automotive makes of our days are challenged to fulfil more and more criteria to remain competitive and financially performant, considering the legislation that must be respected to be able to commercialise each model. One highly important set of rules focus on emissions and strict limits are implemented. To develop compliant products, each make must focus on aerodynamic performance so to reduce the drag of air, thus the required force to overcome for movement at high speeds. While homologation is currently done exclusively as a physical test, to be able to reduce the aerodynamic coefficient, strong virtual tools are used. These measurements performed with computation fluid dynamic software are translated into a virtual wind tunnel that must be able to give relevant and coherent results in respect to final physical validations. The paper will indicate the main types of wind tunnels, parameters to consider, error source and how results can be used. While the computational power is growing each moment, the industry is continuously adapting to obtain the most performant and appealing designs with minimal resources, this being the key of reducing the CO2 footprint of passenger vehicles transport segment.

Modeling of the Dark Phase of Flight and the Impact Area for Meteorites of Real Shapes

Aims. The complex dynamics of bodies, originating from the interplanetary matter and passing through Earth’s atmosphere, defines their further position, velocity, and final location on Earth’s surface in the form of meteorites. One of the important factors that affect the movement of a body in the atmosphere is its shape and orientation. Our goal is to model the interaction of real shape meteoroids with Earth’s atmosphere and compare the results with the standard spherical body approach. Methods. In the simulation, we use 3D models of fragments of the Košice meteorite with different sizes and shapes. Using a 3D model of fragments, we consider the real shape of the body to define its resistance properties during atmospheric transition more specifically. The simulation is performed using virtual wind tunnel in the MicroCFD (Computational Fluid Dynamics) software to obtain more realistic drag coefficients and using the µ(m)-Trajectory software to model the particle trajectory in the atmosphere including the wind profile. The final outputs from these programs are the drag coefficient as a function of the altitude and the particle orientation. Using these parameters we get the more realistic body trajectory and the impact area coordinates. Comparison of the results for real and spherical model meteorite impact location is discussed. Results. Simulation showed significant differences in trajectory and the impact area for the different real body orientations compared to the spherically symmetric body. Also, an important result is a difference in the impact area of the real body with a specific orientation without rotation and the body with considered rotation. The significant difference between the modeled impact of a real shape body and its real place of finding compared to a spherically symmetric body indicates the importance of the method used.

STUDY OF AIRFLOW AROUND SHIP WITH RIGID SAIL ARRAY AND POTENTIAL ARRAY PROPULSIVE POWER

An array of rigid sails installed on a large powered ship could provide a viable means to reduce fuel oil consumption (FOC) and emissions by using the power of the wind as a source of supplementary propulsion. This paper describes the study of airflow around a concept ship design fitted with 14 segment rigid sails (SRS) using a virtual wind tunnel software application and also investigates the propulsive force that a fixed sail array could provide using computational fluid dynamics (CFD) analysis.

Validation of a laminar-turbulent transition prediction technique for a swept-wing boundary-layer flow

The laminar-turbulent transition in the boundary layer of a 45° swept wing model installed at zero attack angle in the test section of a subsonic wind-tunnel was detected with the help of an infrared camera. The camera recorded sequences of frames, the evolution of the preheated model surface temperature acquired and used for differentiating between the laminar and turbulent regions. The transition onset was evaluated at both sides of the model. Corresponding main flow computations in the virtual wind tunnel test section were performed at the same flow conditions with ANSYS Fluent. The computed main-flow velocity profiles along inviscid streamlines were used for analysis of hydrodynamic stability of the boundary layer with respect to Tollmien-Schlichting waves and stationary cross-flow vortices to obtain N-factor distributions along the model chord. A comparison of the experimental and the computed transition onsets was performed.

Investigations of Lift and Drag Performances on Neo-Ptero Micro UAV Models

This paper presents the investigation and improvement of lift and drag characteristics of Neo-Ptero micro-UAV models based on the virtual wind tunnel method. Despite its successful development and flight stability, the lift and drag coefficients characteristics of the current Mark 1 Neo-Ptero remain unknown. To improve the Mark 1 Neo-Ptero performances, Mark 2 Neo-Ptero model has given a new unsymmetrical airfoil wing configuration. The computational aerodynamic analysis was executed and focused on certain lift and drag coefficient characteristics. Lift coefficient results showed that Mark 2 improved in overall lift characteristics such as zero-lift angle, maximum lift magnitude and stall angle magnitude. Conversely, Mark 2 model suffered a slightly higher drag coefficient magnitude and more significant drag increment percentage than Mark 1. However, the trade-off between superior lift magnitude and minor drag generation induced by Mark 2 boosts the model’s aerodynamic efficiency performances but is only limited at early angle stages.

Effects of Different Nose Cone Designs on Trajectory and Impact Angle of Smart Fire Extinguishing Ammunition

A nose cone is the conically shaped tip part of a missile, bomb or aircraft, used to regulate the behavior of oncoming airflow and minimize drag. In this study, the effects of different nose cone designs on the trajectory and impact angle of smart fire extinguishing ammunition were investigated. For this purpose, three different types of ammunition with different nose cone profiles were designed: spherically blunted conic nose cone, spherically blunted tangent ogive nose cone and truncated tangent ogive nose cone. A virtual wind tunnel was created in the computer environment and a CFD software was used to calculate the drag coefficients for each design. By applying Newton's second law of motion, the horizontal distance the ammunition received before striking fire, impact speed, and impact angle were calculated. The obtained results were compared using One-Way ANOVA (analysis of variance) in order to determine whether there is statistical evidence that the associated population means are significantly different. It was determined that the three types of nose cone designs examined did not have a significant effect on the impact speed, impact angle and horizontal distance of the ammunition at the investigated speeds and altitudes. On the other hand, flame detection, distance measurement and impact sensors, which should be in the smart fire extinguishing ammunition, should be on the plane at the front of the ammunition and in contact with the external environment. In order to place these sensors in the nose cone, a truncated tangent ogive nose cone was chosen as the nose cone for the smart fire extinguishing ammunition.

Development of sustainable solutions to sand encroachment on roads in Kuwait using numerical modeling

Site reconnaissance of the threat of sand encroachment in Kuwait outlined major roads that were closed or partially closed for long periods of the year. These roads are AlSubia, AlWafra–Mena Abdallah, and AlWafra-AlZoor. Site surveys of the affected roads were undertaken to investigate the types and thicknesses of accumulated sand layers that were exposed to wind erosion. Soil samples were also collected to assess the particle size distribution. Wind data over the past 35 years were analyzed, which indicated that the prevailing direction is northwest with an average speed of 6–8 m/s. A preliminary concept design based on a composite system of natural and artificial elements was developed to be a sustainable protective system, which included double porous fences and green belts as major elements. Testing of the concept design model was performed in a virtual wind tunnel with different fence porosities and afforestation systems with the aid of the Autodesk Flow numerical model. Virtual wind tunnel results revealed that adopting 50% porosity led to the optimum wind reduction (≈75%), no turbulence area, and maximum sheltered area with no sand accumulation over the fences. The final design adopted was a composite made of artificial fences, green-belt trees, and gravel-stabilized areas, accompanied by removing the street barriers, achieving the aerodynamics concept to provide a long-term sustainable solution for the sand encroachment in those areas.

High-order accurate direct numerical simulation of flow over a MTU-T161 low pressure turbine blade

Reynolds Averaged Navier-Stokes (RANS) simulations and wind tunnel testing have become the go-to tools for industrial design of Low-Pressure Turbine (LPT) blades. However, there is also an emerging interest in use of scale-resolving simulations, including Direct Numerical Simulations (DNS). These could generate insight and data to underpin development of improved RANS models for LPT design. Additionally, they could underpin a virtual LPT wind tunnel capability, that is cheaper, quicker, and more data-rich than experiments. The current study applies PyFR, a Python based Computational Fluid Dynamics (CFD) solver, to fifth-order accurate petascale DNS of compressible flow over a three-dimensional MTU-T161 LPT blade with diverging end walls at a Reynolds number of 200,000 on an unstructured mesh with over 11 billion degrees-of-freedom per equation. Various flow metrics, including isentropic Mach number distribution at mid-span, surface shear, and wake pressure losses are compared with available experimental data and found to be in agreement. Subsequently, a more detailed analysis of various flow features is presented. These include the separation/transition processes on both the suction and pressure sides of the blade, end-wall vortices, and wake evolution at various span-wise locations. The results, which constitute one of the largest and highest-fidelity CFD simulations ever conducted, demonstrate the potential of high-order accurate GPU-accelerated CFD as a tool for delivering industrial DNS of LPT blades.

Aerodynamic Analysis of Hybrid Drone

Drones are Unmanned Aerial Vehicles (UAV’s) or Remotely Piloted Vehicles (RPV’s) whose application ranges from photography to defence. There are two major classifications of drone, one, a fixed wing; and another, a quadcopter. A hybrid drone is a kind of drone which has a mix of features of the two kinds of drone. It has quad-rotors for Vertical Take-Off Landing (VTOL), and a fixed wing for cruise. Aerodynamic analysis for a hybrid drone is done using Computational Fluid Dynamics (CFD) as a tool. A virtual wind tunnel test is done by means of this analysis. It is done in order to examine the various technical edges of the hybrid drone over the rest of the types. Firstly, the main entity of the drone, the wing, of 3 different profiles(aero-foils), is analysed for better lift coefficient as it is the major contributor for the thrust during cruise (for 0 deg angle of attack). The velocity contours are viewed to interpret the aerodynamic advantage of each wing. Then the whole vehicle is analysed after inculcating the wing. The various aerodynamic parameters such as the lift force, lift coefficient, drag force and drag coefficient of the hybrid drone are determined from the analysis. A hybrid drone with optimum lift has been designed from the inference.

Numerical simulations of airflow and convective heat transfer of a sow

Effective ventilation reduces heat stress in sows. A numerical study was carried out to investigate the effects of airspeed and direction on the convective heat transfer around a sow having different postures and body mass. The convection characteristics of a sow were analysed in a virtual wind tunnel using computational fluid dynamics (CFD) tools. The four postures of the standing, sitting, reclining and lateral lying were included. The investigated sow masses ranged from 130 kg to 340 kg. The results show that: 1) The general convective heat transfer was higher when the sow was standing or sitting postures rather than in a reclining or lateral lying posture; 2) Wind direction affects the sow convective heat transfer coefficient. The convective heat transfer coefficient of a sow was largest when it was standing or sitting with the body axis 60° to wind direction. When reclining or lateral lying sow axis at 45° to wind direction, the convective heat transfer coefficient was the largest; 3) The convective heat transfer coefficient of a single sow can be used to predict the convective heat transfer coefficient of a sow amidst rows of multiple sows; 4) Sow body mass negatively affects the convective heat transfer coefficient; 5) The convective heat transfer coefficient of the sow's trunk is relatively low compared with other parts such as the legs, head etc. Based on these results, when a sow needs to be cooled during hot conditions, an oblique airflow is recommended, and airflow speed around the sow's trunk should be increased as much as possible. • Lowest sow heat transfer coefficient in reclining posture compared to others. • Airspeed and direction affected sow convective heat transfer coefficient. • Local convective heat transfer coefficient on trunk lowest compared to others. • Equations for estimating sow's convective heat transfer coefficient established.

Wind impact on low-rise buildings when placing high-rises into the existing development

As height of new development rises, there is an increase in pressure from the windward side and in eddy flows from the leeward side of a high-rise building. This pressure affects not only neighboring high-rises, but also it has an impact on low-rise existing ones. The purpose of the study is to model wind flows to determine maximum aerodynamic wind effects on multi-storey buildings and their surroundings. It also aims at improving the expression for defining maximum wind load depending on the building height and the distance to it. In this study numerical experiments on modeling the distribution of wind flows in a virtual wind tunnel for an existing low-rise building have been carried out. Based on their results, an increasing coefficient in the expression for determining the wind load depending on the height of a multi-storey building and the distance to it is proposed. The results obtained can be used in determining wind loads during the reconstruction of low-rise buildings and their verification calculations when placing multi-storey and high-rise buildings in existing buildings.

Computational Analyses of the Effects of Wind Tunnel Ground Simulation and Blockage Ratio on the Aerodynamic Prediction of Flow over a Passenger Vehicle

With the fast-paced growth of computational horsepower and its affordability, computational fluid dynamics (CFD) has been rapidly evolving as a popular and effective tool for aerodynamic design and analysis in the automotive industry. In the real world, a road vehicle is subject to varying wind and operating conditions that affect its aerodynamic characteristics, and are difficult to reproduce in a traditional wind tunnel. CFD has the potential of becoming a cost-effective way of achieving this, through the application of different boundary conditions. Additionally, one can view wind tunnel testing, be it a fixed-floor or rolling road tunnel, as a physical simulation of actual on-road driving. The use of on-road track testing, and static-floor, and rolling-road wind tunnel measurements are common practices in industry. Subsequently, we investigated the influences of these test conditions and the related boundary conditions on the predictions of the aerodynamic characteristics of the flow field around a vehicle using CFD. A detailed full-scale model of Hyundai Veloster with two vehicle configurations, one with the original and the other with an improved spoiler, were tested using a commercial CFD code STAR-CCM+ from Siemens. Both vehicle configurations were simulated using four different test conditions, providing overall eight different sets of simulation settings. The CFD methodology was validated with experimental data from the Hyundai Aero-acoustic Wind Tunnel (HAWT), by accurately reproducing the test section with static floor boundary conditions. In order to investigate the effect of the blockage ratio on the aerodynamic predictions, the vehicle models were then tested with moving ground plus rotating wheel boundary conditions, using a total of four virtual wind tunnel configurations, with tunnel solid blockage ratios ranging from 1.25%, which corresponds to the actual HAWT, to 0.04%, which presents an open air driving condition.

Analysis of wind-adaptive architecture

As an architectural response to the changing climate, a wind-driven design approach is developed. By adopting the digital design tools, the wind can be integrated into the design process, from the large scale of urban planning, through the form-finding of buildings, as well as designing the texture and roughness of building surfaces. In its more extreme forms, it is even more notable, how the wind flow is shaped and influenced by architecture. Former docks in Stockholm serve as a case study site to test architectural interventions that alter the wind flow on the site. This wind-driven design approach enables the evaluation of the wind performance of various design options, which informs design decisions. Grasshopper, the graphical algorithmic plug-in for Rhinoceros, creates one working environment, where the geometry is parametrically designed, and subsequently analysed in the virtual wind tunnel through the Swift extension for Grasshopper. The Computational Fluid Dynamics analysis results retroactively help decide which of the design options performs the best in the given wind conditions.

STUDY OF THE INFLUENCE OF SECOND ORDER EFFECTS ON THE EXAMPLE OF THE STEEL FRAME OF THE AIRPORT

With the help of modern licensed BIM-information systems of PC Dlubal RSTAB and PC Dlubal RFEM, simulation of stress-strain state and cross-section selection of complex spatial steel structures of the airport, located in Frankfurt am Main (Germany), based on theories 1st and 2nd order effects according to standard DIN EN 1993-1-1-2010 were performed. Spatial steel structures of the airport located in Frankfurt am Main, have been adopted as the object of study. The prototype is the Chennai Airport (India), an architectural concept developed by the American company Frederic Schwartz Architects. The main bearing structures are adopted in the form of spatial steel trusses of complex shape. To determine the cross-sectional dimensions and spacing of the spatial trusses, preliminary calculations were performed. Finally, the step of the spacious trusses was 9 m. The collection of self-weight and imposed loads is carried out in accordance with DIN EN 1991-1-1. The collection of wind loads acting on a complex geometric shape was performed using a virtual wind tunnel and accelerograms, using a CFD analysis of the Dlubal RWIND Simulation PC. To perform CFD analysis, the Dlubal RSTAB PC model was exported to the Dlubal RFEM PC, which made it possible to take into account the presence of external enclosures, overlapping elements and cover, modeled using zero plates, when modeling wind flows. After setting the basic calculation parameters, the model was generated and exported to the Dlubal RWIND Simulation PC. Wind flow simulation in Dlubal RWIND Simulation PC, performed for eight wind directions, of which four most unfavorable were transferred to Dlubal RSTAB PC as separate downloads for further calculation. According to the results of the comparison of the coefficients of the cross-sectional area, it is found that taking into account the effects of the second order, depending on the type of design considered, may lead to the need to increase the estimated cross-sectional area in the range from 22 to 42%. Thus, for complex spatial steel structures, the provisions of the Eurocode standards are confirmed, according to which the consideration of 2nd order effects is obligatory for consideration.

The results of computer analysis of the wind load acting on the set of rolled profiles

The aim of the research is to numerically determine the effect of wind loads on the roof of the rolled profiles of the MIC-120 system. Methods. There were made some calculations in this article of wind load, acting on rolled metal thin-sheet profiles arch and a comparison of computer modeling and buildings requirement such as Building Rules “Loads and Actions” results. The research was carried out by means of modeling of a virtual wind tunnel with the placement to it a metal thin-sheet profiles arch in consideration of different wind actions such as acting on the arch’s butt end (along a generatrix), as well as athwart on the arch and angularly on it with the arch’s width change from 12 to 24 m. The arch modeling as well as the virtual wind tunnel modeling was based on the COSMOSFloWorks software package by means of the method, stated in the previous publications [2; 11]. The theoretical and methodological basis of the research is the Navier - Stokes equation and the equation of the condition of the fluid medium’s components. Results. The results are, first of all, the calculation of the wind pressure on the arch depending on the trajectory, wind speed in different regions and directions of wind flow, secondly, the comparison of the wind pressure, getting with the help of computer modeling with Building Rules 20.13330.2011 “Loads and Actions” and, finally, matching of results of wind pressure for a plain and ribbed arch with equal geometrical parameters, getting by computer modeling. In compliance with the generated calculations there was drawn a conclusion, that the standard pressure according on Building Rules does not change from arch span, but results of the computer modeling show us a change of the wind pressure from the arch’s span.

Aerodynamic features of buildings with runways unit

Currently, opportunities are being developed and are being considered for using flying taxis in large cities due to promising types of air transport (Flying cars, passenger drones). In the second half of the twentieth century, projects for the development of helicopter transport were developed in the UK and the USA. Within the framework of this project, projects for heliports and buildings that interact with helicopter transport were developed in the UK. This experience is very important in the design of buildings with a runway unit, interacting with advanced air transport. Based on an analysis of projects in the UK and the USA, the authors developed experimental aerodynamic schemes of buildings with a landing unit. These projects were tested in the Virtual Wind Tunnel and implemented with the recommendations received by the authors at TsAGI (Central Institute of Aero hydrodynamics). In architectural design of buildings interacting with air transport, aerodynamics is the most important tool for shaping the spatial and compositional solutions of architectural objects.

Исследование способов испытания лопаточных диффузоров центробежных компрессорных ступеней в виртуальной аэродинамической трубе

A mathematical model of a vaned diffuser of a centrifugal compressor stage can be constructed based on the results of mass CFD-calculations, similar to that of vaneless diffusors. The methods for calculating the annular cascade and the straight cascade differ due to the existence of vaneless diffusor sections in front of the cascade and behind it. The rational dimensions of these sections are determined. The calculations of two-dimensional cascades without restricting walls appear to be irrational. The calculation is effective for a sector with one vane channel, a moderate number of cells, and the turbulence model k–ε. Averaging the flow parameters at the blade cascade exit leads to ambiguous results. To calculate the characteristics of the blade cascade, the parameters in a section with a diameter equal to 1.85 of the diameter of the blade cascade exit should be used. In domestic and foreign literature, it is customary to emphasize the effectiveness of the CFD methods that replace physical experiments. Calculations of the compressor stages are called virtual rig testing, while those of the blade cascade are known as virtual wind tunnel testing. To study stationary flow, as a virtual wind tunnel, it suffices to consider the blade cascade itself, the preceding and the subsequent vaneless spaces.

Using BIM and Virtual Wind Tunnel To Investigate Wind Induced Loads On Steel Agriculture Buildings

Using BIM and Virtual Wind Tunnel To Investigate Wind Induced Loads On Steel Agriculture Buildings

CFD-calculation method for vane diffusers of a centrifugal compressor stage

Centrifugal process compressors consume huge amount of energy. The gas dynamic design methods are based on physical and numerical experiments. The methods improvement is an actual task. The theory of subsonic axial compressors is based on the results of wind tunnel tests of straight blade cascades. The modern trend is to substitute physical experiments with CFD calculations. There is positive experience of vaneless diffuser virtual wind tunnel test results (CFD calculations) that are inserted in the math model for compressor characteristic simulation. CFD calculations of vane diffusers also can be used to improve math model of a centrifugal stage but the calculation technology is more complicated. The Authors have investigated the problem and propose rational solution.

CFD prediction of convective heat transfer and pressure drop of pigs in group using virtual wind tunnels: Influence of grid resolution and turbulence modelling

Ventilation for the animal house is important since it is highly linked with the convective heat removal from animals. In this context, the animals as obstacles affect the ventilation airflow and consequently the air distribution within Animal Occupied Zone (AOZ). To study the convective heat transfer (CHT) of animals and the pressure drop (PD) resulting from the animals, computational fluid dynamics (CFD) can be an efficient tool, particularly in comparison with experimental methods. However, simulation accuracy is influenced by grid treatment and the choice of turbulence models. To reveal the grid effects on CHT and PD, fifteen 3D meshes with different facial grids sizes (0.04 m, 0.02 m, and 0.008 m) and prismatic layer thicknesses (PLT) (0 m, 0.0015 m, 0.009 m, 0.02 m, 0.04 m) were tested based on staggered tube bundle models representing simplified bluff bodies using virtual wind tunnels. Then, four commonly used turbulence models, namely, standard k–ɛ, realisable k–ɛ, standard k–ω, and SST k–ω, together with two wall treatments were evaluated and compared with the empirical calculation. The evaluation of turbulence models and wall treatment was then carried out based on grouped pig models using virtual wind tunnels. The results showed that the PLT could be an important influence on the stability of the simulation with varied facial grid sizes. The k–ω models performed better than the k–ɛ models on the predictions of both the CHT and the PD based on the tube bundle model. Wall function provided acceptable results on CHT, however, significant flaws on the PD on both tube bundles and pig models.