Aerodynamic Investigation Research Articles

Numerical investigation of full scale coaxial main rotor aerodynamics in hover and vertical descent

The original free vortex wake model was used for numerical investigation. Calculation of the aerodynamic characteristics in hover and vertical descent modes in the range of vertical descent speed of 0–30 m/s including the Vortex Ring State (VRS) area was performed. The calculations were carried out under the condition of variable blade pitch angle values providing a fixed time-average thrust value. Visualization data of free vortex wake shapes, flow structures, and velocity fields were obtained and analyzed. The time-dependences of the rotor’s thrust and torque coefficients were obtained and analyzed. The obtained data allows determining the boundaries of the VRS area by various criteria such as rotor thrust and torque pulsations, growth of rotor power consumption relative to the hover, growth of rotor induced velocities relative to the hover, and growth of the required rotor blade pitch angles values. The results of the study are compared with experimental and calculated data of other authors and can significantly supplement the available results of experimental and computational studies in this area.

Adaptable test rig for two-stage axial turbine

This contribution describes a new test rig for a two-stage axial turbine built in the VZLÚ. The test rig has replaced an original facility used for a full stage aerodynamics investigation. The motivation for the design of the new test facility was the limitations of the original one. The design is briefly discussed, and then the first measurement results are presented. The first operation was performed with a turbine stage already measured in the original facility. This allows the comparison of the most important quantities.

Shape and Spacing Effects on Curvy Twin Sail for Autonomous Sailing Drone

There is a growing interest this paper for ocean sensing where autonomous vehicles can play an essential role in assisting engineers, researchers, and scientists with environmental monitoring and collecting oceanographic data. This study was conducted to develop a rigid sail for the autonomous sailing drone. Our study aims to numerically analyze the aerodynamic characteristics of curvy twin sail and compare it with wing sail. Because racing regulations limit the sail shape, only the two-dimensional geometry (2D) was open for an optimization. Therefore, the first objective was to identify the aerodynamic performance of such curvy twin sails. The secondary objective was to estimate the effect of the sail’s spacing and shapes. A viscous Navier-Stokes flow solver was used for the numerical aerodynamic analysis. The 2D aerodynamic investigation is a preliminary evaluation. The results indicated that the curvy twin sail designs have improved lift, drag, and driving force coefficient compared to the wing sails. The spacing between the port and starboard sails of curvy twin sail was an important parameter. The spacing is 0.035 L, 0.07 L, and 0.14 L shows the lift coefficient reduction because of dramatically stall effect, while flow separation is improved with spacing is 0.21 L, 0.28 L, and 0.35 L. Significantly, the spacing 0.28 L shows the maximum high pressure at the lower area and the small low pressure area at leading edges. Therefore, the highest lift was generated.

Numerical Aerodynamic Investigation of Exhaust Diffuser for Powerful Steam Turbine in a Wide Operating Modes Range

The objectives of research done were to define the aerodynamic characteristics of the different axial-radial diffusers constructions on load-changing turbine operations with the purpose to find their aerodynamic improvement reserve. Using the CFD program, the numerical analysis of aerodynamic characteristics has been performed for the four options of outlet axial-radial diffusers used for the steam turbine K-325-23,5. The flow for all four options of the diffuser was calculated for preset constant total pressure and total temperature at the channel input and the static pressure at the diffuser output. The data was taken from experiment that had been performed by department of turbine construction of NTU “KhPI”. A comparative analysis of the aerodynamic characteristics of the diffusers was performed and the values of the coefficients of total losses were defined. A version of the outlet axial-radial diffuser was suggested for the turbine that provides the lowest coefficient of total losses and better flow distribution through entire channel.

CFD investigation of unsteady aerodynamics in gas turbine engine blade surface

Abstract The problem of unsteady excitations is quite common in turbomachinery as they're subject to dynamic conditions. These unsteady excitations induced in turbomachinery result in forced dynamic response and leading the fatigue failure of aircraft engine components. In this paper unsteady aerodynamic mechanism that governs, the forced response in the stator - rotor interaction of turbine stages is investigated. Two-dimensional numerical investigations to calculate the pressure distribution along with the rotor blade profile. The surface mid-span coordinates of the first stage stator-rotor are molded according to the open-source NACA geometry Coordinates. To predict the excitation forces acting on the rotating rotor blades function of time-resolved computation is carried. The pulsating pressure distribution along the stator-rotor interaction and excitation forces along the intra-blade-row is computed using the Fluent.

Predictive analyses for aerodynamic investigation of curtain walls

The paper investigates structural deformation of a stick curtain wall system under full-scale experimental tests. In particular, the wind-façade interaction is discussed through data given by a wind tunnel campaign. European standards for assessment of façades generally foresee to check façade air permeability and wind action resistance by applying a uniformly distributed pressure over the surface. These are unrealistic tests since it is well known that wind distribution can be affected by the building aerodynamics and atmospheric turbulence that generally result in a not uniformly distributed pressure over a surface. In addition, maxima and minima are not simultaneous during wind flow action. This generates an out-of-plane torsion of façade transoms caused by different deformation of the mullions. Elastomeric gasket deformation, as a consequence, may increase façade air permeability. This aspect is neglected by current codes. To investigate this aspect, a numerical FE model was calibrated by full-scale experimental tests and analyses were carried out to compare façade deformation under pressure tests. Six different load combinations were proposed through the investigation of spatial correlation of pressure coefficients time histories acquired in wind tunnel tests on sixteen different geometries of building and two wind angles. In particular, buildings with rounded and angular plan shapes were investigated. Results show a significant difference in structural deformation of the façade between the six load conditions and in particular, a noteworthy deformation between adjacent mullions causing torsion of the transom connected to them.

Double multiple stream tube theory coupled with dynamic stall and wake correction for aerodynamic investigation of vertical axis wind turbine

This study describes an effectively analytic methodology to investigate the aerodynamic performance of H vertical axis wind turbine (H-VAWT). An in-house code based on double multiple stream tube theory (DMST) coupled with dynamic stall and wake correction is implemented to estimate the power coefficient. Design optimization of airfoil shape is conducted to study the influences of the dynamic stall and turbulent wakes. Airfoil shape is universally investigated by using the Class/Shape function transformation method. The airfoil study shows that the upper curve tends to be less convex than the lower curve in order to extract more energy of the wind upstream and generate less drag of the blade downstream. The optimal results show that the power coefficient increases by 6.5% with the new airfoil shape.

Improved Form Factor for Drag Estimation of Fuselages with Various Cross Sections

The paper presents an aerodynamic investigation of 70 different streamlined bodies with fineness ratios ranging from 2 to 10. The bodies are chosen to idealize both unmanned and small manned aircraft fuselages and feature cross-sectional shapes that vary from circular to quadratic. The study focuses on friction and pressure drag in dependency of the individual body’s fineness ratio and cross section. The drag forces are normalized with the respective body’s wetted area to comply with an empirical drag estimation procedure. Although the friction drag coefficient then stays rather constant for all bodies, their pressure drag coefficients decrease with an increase in fineness ratio. Referring the pressure drag coefficient to the bodies’ cross-sectional areas shows a distinct pressure drag minimum at a fineness ratio of about three. The pressure drag of bodies with a quadratic cross section is generally higher than for bodies of revolution. The results are used to derive an improved form factor that can be employed in a classic empirical drag estimation method. The improved formulation takes both the fineness ratio and cross-sectional shape into account. It shows superior accuracy in estimating streamlined body drag when compared with experimental data and other form factor formulations of the literature.

Aerodynamic Investigation of a Morphing Wing for Micro Air Vehicle by Means of PIV

A wind tunnel tests campaign has been conducted to investigate the aerodynamic flow around a wing morphing to be used in a micro air vehicle. Non-intrusive whole field measurements were obtained by using PIV, in order to compare the velocity and turbulence intensity maps for the modified and the original version of an adaptive wing designed to be used in a micro air vehicle. Four sections and six angles of attack have been tested. Due to the low aspect ratio of the wing and the low Reynold number tested of 6.4 × 104, the influence of the 3D effects has been proved to be important. At high angles of attack, the modified model prevented the detachment of the stream, increased the lift of the wing and reduced the turbulence intensity level on the upper surface of the airfoil and in the wake.

Aerodynamic investigation of twist angle variation based on wing smarting for a flying wing

In this paper, the effects of twist angle variation on aerodynamic coefficients and flow field on the wing with wing smarting approach are studied using numerical simulation. The simulation was performed using incompressible Reynolds-Averaged Navier-Stokes (RANS) equations based on the two-equation k-ω Shear Stress Transport (SST) turbulent model for flow speed 30 m/s and a Reynolds number of 69000. Investigations have been carried out for several twist angles and at a specific range of angles of attack. The twist applied is the type of geometric twist (wash-out), which is linearly distributed along the span. The test case is a lambda-shaped tailless aircraft with a wing fracture on the trailing edge, and a sweep angle 56°. The results show that with increasing twist angle, the aerodynamic efficiency improves over a wide range of angles of attack, but at 0° angle of attack it will decrease significantly. By increasing the angle of attack, the effect of twist on the flow field and aerodynamic coefficients will gradually decrease; hence, at a certain amount of angle of attack, the effect of twist will stop, that angle is called the neutral brink angle. Longitudinal stability analysis shows that by growing the twist angle, the conditions required for longitudinal stability are satisfied, and the pitch-up phenomenon will be delayed.

Aerodynamic investigation of the shock train in a scramjet with the effects of backpressure and divergent angles

AbstractNumerical simulations are carried out to study the effect of divergence angle and adverse pressure gradient on the movement of a shock wave train in a scramjet isolator. The commercial software tool ANSYS Fluent 16 was used to simplify the two‐dimensional Reynolds‐averaged Navier‐Stokes equation with the compressible fluid flow by considering the density‐based solver with the standard k‐ε turbulence model. The species transport model with a single‐step volumetric reaction mechanism is employed. Initially, the simulated results are validated with experimental results available in the open literature. The obtained results show that the variation of the divergence angle and backpressure on the scramjet isolator has greater significance on the flow field. Also, with an increase in the backpressure, due to the intense turbulent combustion, the shock wave train developed should expand along the length and also move towards the leading edge of the isolator leading to a rapid rise in the pressure so that the pressure at the entrance of the isolator can match the enhanced backpressures.

Aerodynamic investigation of the start-up process of H-type vertical axis wind turbines using CFD

In this study, a CFD start-up model has been built after conducting the sensitivity studies to evaluate the self-starting behaviour of the H-type vertical axis wind turbines (VAWTs). The self-starting behaviour of a well-investigated VAWT is used for the model validation, and then the details of aerodynamics of the start-up process have been examined. Finally, the effect of the moment of inertia and the blade number on the aerodynamic behaviour of the self-starting and power performance of the H-type VAWT are analysed. It has been found that in the critical region, where TSR<1, the contribution of the drag to the torque generation plays a significant role in the second and third quarters of the rotor revolution, where the azimuthal position varies between 100° and 253°. The results also show that increasing the turbine inertia did not show a noticeable effect on the start-up behaviour of the turbine and final rotational speed. However, an increase in the instantaneous turbine power during the start-up process after the optimum TSR is observed with decreasing the turbine inertia. The current findings also show that an increase in the blade number makes the turbine easier to start-up; however, this may reduce the turbine power coefficient.

Aerodynamic Investigation on Performance Enhancement of NACA 2412 Airfoil with Suction Assistance

Advanced transport aircraft concept has active boundary-layer control by slot suction which reduces drag by stabilizing the laminar boundary. Thus, the prevention of transition and delaying the boundary layer separation will lead to a higher lift co-efficient. The influence of location and position of suction, suction flow rate and suction hole width on aerodynamic performance have greater influence. These examine the potential payoff for boundary-layer control as applied to the advanced-concept wings. An experimental work deals with the continuous normal suction from the wing upper surface effects on the aerodynamic forces. The wing model with NACA-2412 has been made to achieve normal suction from the wing upper surface by means of four slot channels. The results showed that the continuous normal suction can significantly increase the lift to drag force ratio and this ratio is increasing as the strength of suction increases. There is a convincing decrease in drag and pressure loss and an increase in max lift, which in turn improves the overall performance of the aircraft. While multi-hole suction control can reduce drag much more efficiently than single hole suction control, the position of the suction hole has a greater effect on reducing pressure losses than the suction flow rate.

Investigation of aerodynamics of separator delivery from cavity

The ejection test technology is studied in a sub-transonic supersonic wind tunnel using a single cylinder to provide ejection velocity. The angular velocity adjusting device of ejection mechanism is designed, which can adjust the ejection velocity and angular velocity of the model independently. When the ejection cylinder moves downward, the angular velocity adjusting mechanism works at the same time, so that the model has the preset ejection velocity and angular velocity at the moment of leaving the ejection frame. The ejection velocity error is less than 5%, the angular velocity error is less than 10%, and the repetition rate is more than 95%. The new technology has been verified by wind tunnel tests under complex aerodynamic conditions of sub-transonic supersonic and multi-body interference. All parameters have reached or surpassed the existing technical specifications. It has served for model tests many times and met the needs of wind tunnel test research on ejection of embedded weapons in aircraft.

The GTU: A New Realistic Generic Pickup Truck and SUV Model

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Traditionally, ground vehicle aerodynamics has been researched with highly simplified models such as the Ahmed body and the SAE model. These models established and advanced the fundamental understanding of bluff body aerodynamics and have generated a large body of published data, however, their application to the development of passenger vehicles is limited by the highly idealized nature of their geometries. To date, limited data has been openly published on aerodynamic investigations of production vehicles, most likely due to the proprietary nature of production vehicle geometry. In 2012, Heft et al. introduced the realistic generic car model ‘DrivAer’ that better represents the flow physics associated with a typical production vehicle. The introduction of the DrivAer model has led to a broad set of published data for both experimental and computational investigations and has proven itself invaluable as a correlation and calibration tool of wind tunnels, the validation of computational fluid dynamics (CFD) codes and increasing the understanding of the fundamental flow physics around passenger vehicles.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;Automotive sales trends in the United States, published by the Bureau of Economic Analysis in 2018, indicate that sales of Pickup Trucks (PUs) and Sports Utility Vehicles (SUVs) have increased over the past 10 years and are outselling sedans at a rate just over two to one. Compared to sedans, PU and SUV body styles pose additional aerodynamic challenges due to their complex wake structures. The introduction of a realistic generic PU and SUV model as an open access tool is expected to yield benefits to the wider community, equivalent to those of the DrivAer passenger vehicle. This paper introduces the Generic Truck Utility (GTU) as a realistic, generic PU truck and interchangeable SUV model. The paper will focus on the design and development of the GTU and will present a summary of preliminary experimental results of the GTU complemented by numerical simulations using iconCFD®, an open source based CFD solver.&lt;/div&gt;&lt;/div&gt;

Aerodynamic Investigation of Datum and Slotted Blade Profiles under Different Mach Number Conditions

Mach number effects on loss and loading are evaluated in both the datum and slotted compressor profiles under a wide range of incidences based on two-dimensional (2D) computational fluid dynamic (CFD) simulations. First, total pressure loss and loading abilities are compared. Then, three kinds of deficit thickness are defined and evaluated, and a correlation is made between the loading and the momentum deficit thickness at the profile trailing edge. Finally, the nondimensionalized destruction of mean mechanical energy and dissipation function are employed to analyze the loss mechanism. The slotted profile broadens the low loss range towards the positive incidence range. The slotted profile allows a higher diffusion factor (DF) than the datum profile. It is hard to distinguish failure simply based on the DF values, whereas the Zweifel loading coefficient connects well with the low momentum deficit in the profile trailing edge. The peak of the V-shaped distributions in the Ψ - θ d e f plot could better suggest the design condition and determine the correct operating range despite the occurrence of bulk separation. The slotted profile gains the ability of the boundary layer flow near the suction surface to resist the adverse pressure gradient, hence, a reduced shear thickness and a uniformed downstream flow field is obtained.

Comparative Study on Several Type of Turbulence Model Available in ANSYS-Fluent Software for ONERA M6 Wing Aerodynamic Analysis

ONERA M6 wing model is definitive computational fluid dynamic (CFD) validation case for aerodynamic investigations. Therefore, such investigation on aerodynamic characteristics is conducted with commercial CFD software known as ANSYS-Fluent software. The advantages of this software beside offer various flow solvers, this software also provides a various type of Turbulence Models can be implemented. In the present works, an investigation on capabilities of turbulence models available in the ANSYS-Fluent software based on Boussinesq hypothesis had been studied. The investigation had used five ty pe Turbulence Models for evaluating the aerodynamic characteristics of the ONERA M6 wing model. These five turbulent models are: (1) Spalart-Allmaras, (2) k-ε Standard, (3) k-ε Realizable, (4) k-ω Standard and (5) k-ω SST turbulence models. The flow analysis are carried at two different angle of attacks namely at α = 3.060 and α = 6.060. These two angle of attacks correspond with Mach number 𝑀𝑀∞= 0.84 and the Reynolds number Re = 11.76×106. The comparison between ANSYS software with the experimental result as provided by AGARD AR-138 in term pressure coefficient distribution at several wing span location and overall aerodynamics characteristics in term lift coefficients shows that among those five turbulence models had been found that Spalart-Allmaras and k-ω SST turbulence model gives result close to the experimental results and the smallest number of iteration for getting a converge solution.

Evaluation of variable pitot inlet concepts for transonic and supersonic civil aviation

Purpose This paper aims to describe the selection of the ideal variable inlet concept group by using results of aerodynamic investigations, system safety analyses and integration studies. Design/methodology/approach Aerodynamic and functional inlet requirements are explained and variable inlet concept groups are introduced. The concept evaluation by means of a weighted point rating is presented. The respective concept groups are analysed and evaluated regarding economic, functional and safety requirements. Findings By means of this evaluation, the concept group that adjusts the inlet geometry by rigid segment repositioning is identified as most suitable concept group. Originality/value The early selection of the most suitable concept group enables more detailed subsequent concept investigations, potentially enabling the technology of variable inlets for future commercial aircraft.

Multi-disciplinary design and performance assessment of effective, agile NATO air vehicles

This article belongs to a series of publications about the activities performed within the NATO STO Research Task Group AVT-251 on “Multi-Disciplinary design and performance assessment of effective, agile NATO Air Vehicles”. The article concentrates on the development and investigation of the MULDICON UCAV configuration, as well as on the organization and assessment of the AVT-251 task group itself. After a brief introduction to the preceding task groups and the research questions that lead to AVT-251, the selection of design requirements is discussed and the chosen way for developing MULDICON out of its predecessor, the SACCON concept, is sketched. A special focus is placed on the various aerodynamic investigations with the aim to control the vortex flow topology at medium to high angles of attack. Thereafter, the overall aircraft design work on the re-designed outer shape is presented and the resulting MULDICON configuration is investigated and assessed. Finally, a concluding summary of the MULDICON concept and the AVT-251 task group is presented.

Aerodynamic and aeroacoustic investigation of an innovative regional turboprop scaled model: numerical simulations and experiments

An extensive aeroacoustic and aerodynamic investigation of an innovative regional turboprop aircraft has been carried out experimentally and numerically under the framework of two research projects funded by the European Union through the CleanSky Research Programme. Experimental tests have been performed in the RUAG Large Subsonic Wind Tunnel in Switzerland and CFD results have been validated against the experimental data. The A/C high-lift performance, stability and control derivatives, aerodynamic noise sources, and low-noise solutions for high-lift devices, have been investigated under representative conditions in cruise, take-off, and landing configurations. The aerodynamic and aeroacoustic investigation has been carried out parametrically, in terms of several reference quantities, including the propellers’ thrust and rpm, the speed of the air-flow, the incidence angle of the aircraft and the position of the microphone array used for the acoustic investigation. The present paper gives an overview of relevant results obtained for selected aircraft configurations which have been tested in the wind tunnel and analyzed through CFD simulations. The focus lies on the overall aerodynamic characterization and on the noise sources identification carried out using standard beamforming techniques.