Aerodynamic Regime Research Articles

Numerical analysis of aerodynamic regime near tailings storage facility

Tailings formed during the mining and beneficiation of iron ore are sources of intensive dust generation. In order to assess the intensity of dust formation and determine the effectiveness of methods of its reduction, it is necessary to know the local velocity of the air flow near the various surfaces of the tailings storage facility. For the theoretical solution of this problem, a CFD model was developed, which allows determining the velocity field of the air flow when flowing around the tailings storage facility. The model allows you to obtain the value of the wind speed near the surfaces of the structure and, based on this information, to make a forecast of possible dust formation. The constructed CFD model is based on the use of an aerodynamic model of potential motion. The modeling equation is the Laplace equation for the velocity potential. To build a numerical model, the idea of establishing a solution in time is used, therefore numerical integration of the “unsteady equation” for the velocity potential is carried out. Numerical integration is carried out using the finite-difference method of total approximation. The results of the computational experiment are presented.

Determination of characteristics of grain movement in the presence of dry friction forces and resistance of the environment

Purpose. Determination of the effect of air resistance on the parameters of particle movement on rough surfaces and determination of the particle movement resistance coefficient. Methods. Based on the analysis of modern ideas about the mechanisms of the formation of hydrodynamic (aerodynamic) resistance of the environment during the movement of a solid body, the form of recording the resistance force (formalization of the resistance force) is determined, and in accordance with the accepted form of representation of the resistance force, which depends on the aerodynamic regime (Reynolds number), the equation of motion is formulated along the surface in a stationary or moving air environment according to the value of the active forces. To identify the constant coefficients of differential equations, their analytical (symbolic) solution is obtained in the form of dependences of displacement S on time t. The coefficients included in the equation are determined from the experimental data (direct measurements of S and t) from the dependences of S(t). The movement of a single particle or several connected particles along a real surface (smooth, artificially rough, perforated, etc.) of a plane inclined to the horizon at an angle α was used as a model of physical and virtual experiments. The size of the angle α changes the speed of movement of the particle and the time it stays on the plane. Results. Theoretical and experimental studies of the movement of particles of grain material along sloping surfaces (feeding device) were carried out, which made it possible to determine the characteristics of the movement of the material: speed of movement, speed of descent of the grain from the support surface, coefficients of friction and aerodynamic resistance for different groups of grain material. Conclusions. The coefficients of friction and aerodynamic resistance of the air medium determined by the proposed method make it possible to use known theoretical mathematical models to calculate the parameters of particle movement on an inclined plane with maximum accuracy. Keywords: grain material, support-slope surface, speed of grain movement, coefficient of friction, aerodynamic resistance, equation of dynamic movement of grain.

Transonic Aerodynamic Analysis of Different Forebody Shapes of Aerospace Vehicles

One of the most important features of an aerospace vehicle design is its shape, especially the forebody part, since it defines the main characteristics of the vehicle aerodynamic. In this context, the present work has the purpose of investigating the transonic aerodynamic regime in typical vehicle models, with different frontal geometry configurations, using the experimental techniques pressure sensitive paint (PSP) and Schlieren. The aim is to get more insights about the flow patterns over the selected models, regarding the transonic regime, in terms of qualitative density field evaluation, and the identification of important aerodynamic parameters, such as shock wave positioning and pressure gradients over the model, as well as the influence of the forebody configuration in the flow pattern. The test campaign was carried out in the Pilot Transonic Wind Tunnel of the Institute of Aeronautics and Space (IAE; in Portuguese, Instituto de Aeronáutica e Espaço), varying Mach numbers from subsonic to low supersonic. Five forebody configurations mounted in a cylindrical body having the standard cone-cylinder shape as baseline was considered. A description of the phenomena occurring around and on the models surface for all five models is presented, through analyses of the Schlieren images and PSP results.

Transparent Elemental Facade with an Integrated Ventilation Unit for a High-Rise Building – Development and Experimental Verification

Abstract The article documents the development of a modular transparent elemental facade. The cooperative development was realized in two areas, i.e., the development of facade ventilation units for an under-pressure ventilation system and experimental verification in a laboratory of a facade panel and optimization of its acoustic parameters. The task of controlled ventilation in modern residential buildings is to ensure the optimum quality of the interior environment and fulfill hygienic and thermal technical requirements that guarantee the comfort of the users. The paper discusses the development and experimental verification of atypical vertical ventilation units of an under-pressure controlled ventilation system for a residential high-rise building. A recommended concept for the facade´s details has been developed in relation to the ventilation system. Conceptual designs of alternatives to the air inlet openings of an under-pressure controlled ventilation system for the apartments with an atypical vertical geometry were proposed. An optimized alternative to air inlet openings in the bottom level of a vertical pilaster with the function of an air distribution channel for a ventilation system has been selected and developed. Laboratory experiments have verified the physical properties of the optimized alternative ventilation units of the under-pressure controlled ventilation system in their development cycle. The hydrodynamic regime of the air inlet openings of the controlled ventilation system has been verified by experimental research in a laboratory large rain chamber. The aerodynamic regime of a naturally controlled ventilation system was verified by experimental research in a large laboratory pressure chamber. The acoustic properties of the naturally controlled ventilation system were verified by experimental research in a laboratory´s acoustic chambers. The verified parameters of the ventilation units of the under-pressure controlled ventilation obtained by the experiment were compared with the design parameters. An experimental assessment of the mechanical, thermal and acoustical parameters of the elemental modular facade was carried out in a laboratory. At the end of the article, the results and conclusions of the laboratory experiment are summarized.

Numerical observation of secondary Mach stem in weak acoustic shock reflection.

Recently Ram, Geva, and Sadot [J. Fluid Mech. 768, 219-235 (2015)] showed, experimentally, the formation of a secondary Mach stem generated from the reflection of the primary Mach stem in the aerodynamic regime. Such a phenomenon has never been observed, either experimentally or numerically, in the framework of weak acoustic shocks. In this work, the formation of a secondary Mach stem is observed from the reflection of acoustic shock waves on a convex-concave boundary giving rise to a complex five-shock pattern. This study is fully numerical and is based on the numerical solution of a nonlinear acoustic system of equations using a recently developed discontinuous Galerkin solver.

Study of the aerodynamic regime of the cooling system of the foundations of buildings on the filling soil in the conditions of the Far North

During construction in the Far North, due to the preservation of permafrost soils, the buildings are arranged on piles and foundations on the bedding soil. In the foundations of buildings for a smaller impact on the ground and prevention from defrosting of the soil, air cooling systems with cooling pipes are provided. Seasonal and daily variations in the temperature of the outside air and intensity of solar radiation cause fluctuations in the temperature regime of the upper layers of the soil. As a result of transformation of natural soils into technogenic, its physical properties change significantly when exposed to negative temperatures. Freezing of the soil thawed out over the summer and its further cooling is achieved by passing cold air in the winter through the air channels. The cooling system must provide the position of the upper surface of the frozen soil state under the building, as adopted by the project. This paper discusses the aerodynamic mode of the air cooling system for foundations on bedding in permafrost soils during the construction of various buildings and structures while preserving the base soils in a frozen state and using natural cold of the outside air, which will improve the reliability of permafrost bases. An engineering method has been developed for calculating the heat fluxes of soil and pipeline laid in thickness. A technique for engineering calculation of change in the thermal regime depending on the parameters of the outside air is given, which will make it possible to usefully use the energy of the cold enclosed in the ground to warm the outside air.

Assessment of Transition Modeling and Compressibility Effects in a Linear Cascade of Turbine Nozzle Guide Vanes

The flow field in a linear cascade of highly loaded turbine nozzle guide vanes (NGVs) has been numerically investigated at low and high-subsonic regime, i.e., exit isentropic Mach number of M2is = 0.2 and 0.6, respectively. Extensive experimental data are available for an accurate assessment of the numerical procedure. Aerodynamic measurements include not only vane loading and pressure drop in the wake but also local flow features such as boundary layer behavior along both pressure and suction sides of the vane, as well as secondary flow structures downstream of the trailing edge (TE). Simulations were performed by using two computational fluid dynamics (CFD) codes, a commercial one and an open-source based in-house code. Besides computations with the well-established shear-stress transport (SST) k–ω turbulence model assuming fully turbulent flow, transition models were taken into account in the present study. The original version of the γ–Reθ model of Menter was employed. Suluksna–Juntasaro correlations for transition length (Flenght) and transition onset (Fonset) were also tested. The main goal was to establish essential ingredients for reasonable computational predictions of the cascade aerodynamic behavior, under both incompressible and compressible regime. This study showed that transition modeling should be coupled with accurate profiles of inlet velocity and turbulence intensity to get a chance to properly quantify aerodynamic losses via CFD method. However, additional weaknesses of the transition modeling have been put forward when increasing the outlet Mach number.

Development and Experimental Verification of Ventilation Units for Under Pressure Ventilation System

Task of controlled ventilation in modern residential buildings is to ensure optimum quality of interior environment and fulfill hygienic and thermal technical requirements guaranteeing comfort of user. The paper discusses development and experimental verification of atypical vertical ventilation units of under pressure controlled ventilation system for residential high-rise building. Recommended concept of solution to façade detail in relation to ventilation system. Conceptual designs of alternatives of air inlet openings of under pressure controlled ventilation system for apartments of atypical vertical geometry. Optimized alternative of air inlet openings in the bottom level of vertical pilaster with function of air distribution channel for ventilation system. Laboratory experimental verification of physical properties of optimized alternative of ventilation units of under pressure controlled ventilation system in their development cycle. Hydrodynamic regime of air inlet openings of controlled ventilation system – laboratory experimental research in large rain chamber. Aerodynamic regime of natural controlled ventilation system – laboratory experimental research in large pressure chamber. Acoustic properties of natural controlled ventilation system – laboratory experimental research in acoustic chambers. Comparison by the experiment of verified parameters of ventilation units of under pressure controlled ventilation with design parameters.

New Façade Ventilation Units of under Pressure Controlled Ventilation System

Task of controlled ventilation in modern residential buildings is to ensure optimum quality of interior environment and fulfill hygienic and thermal technical requirements guaranteeing comfort of user. The paper discusses development and experimental verification of atypical vertical ventilation units of under pressure controlled ventilation system for residential high-rise building. Recommended concept of solution to façade detail in relation to ventilation system. Optimized alternative of air inlet openings in the bottom level of vertical pilaster with function of air distribution channel for under pressure controlled ventilation system. The paper discusses laboratory experimental verification of physical properties of optimized alternative of ventilation units of under pressure controlled ventilation system for high-rise residential building in their development cycle. Boundary conditions of physical designing of envelope structures for load of wind-driven rain and their modifications for high-rise building in the locality of Bratislava. Hydrodynamic regime of air inlet openings of controlled ventilation system – maintaining water impermeability of air inlet openings of the ventilation system under the effect of wind-driven rain – laboratory experimental research in large rain chamber, its results and necessary construction modifications of elements of ventilation units. Aerodynamic regime of natural controlled ventilation system – quantification of volume of air flow rate through ventilation units in dependence to air pressure difference - laboratory experimental research in large pressure chamber. Acoustic properties of natural controlled ventilation system – quantification of index of air impermeability of controlled ventilation system in open and closed position - laboratory experimental research in acoustic chambers. Comparison by the experiment of verified parameters of ventilation units of under pressure controlled ventilation with design parameters.

Inherent Stability Modes of Low-Aspect-Ratio Wings

The development of micro aerial vehicles has been hindered by a poor understanding of the flight dynamics associated with the unique aerodynamic regime. This study experimentally estimates the aerodynamic damping derivatives of flat-plate wings with aspect ratios less than 3 at a Reynolds number of ; when combined with previously published results detailing the lateral and longitudinal static loads, a dynamic model is developed for low-aspect-ratio wings. The initial-condition response of the linear equations of motion shows that the loading created by roll stall results in purely aerodynamic lateral modes which, unlike conventional aircraft, are not attributed to geometric features, such as the vertical tail; this response was favorably compared with the integration of the full nonlinear equations. The mode is manifested by divergent, high-amplitude perturbations in sideslip, bank angle, and roll rate; furthermore, it is seen to be affected by angle of attack variations, which significantly alter the instantaneous value of the roll stability derivative . If the input frequency of the angle of attack oscillations is close to the natural frequency of the pure lateral mode, the bank angle is seen to drift away from its equilibrium value due to an attenuated restoring roll moment. This represents a previously unconsidered stability mode, referred to as roll-resonance, which couples the lateral and longitudinal stability axes for small perturbations from equilibrium flight conditions.

A Computational Investigation of Unsteady Aerodynamics of Insect-Inspired Fixed Wing Micro Aerial Vehicle’s 2D Airfoil

A Micro air vehicle (MAV) is defined as class of unmanned air vehicle (UAV) having a linear dimension of less than 15 centimeters and a mass of less than 100 grams with flight speeds of 6 to 12 meters per second. MAVs fall within a Reynolds number (Re) range of 50,000 and 120,000, in which many causes of unsteady aerodynamic effects are not fully understood. The research field of low Reynolds number aerodynamics is currently an active one, with many defence organizations, universities, and corporations working towards a better understanding of the physical processes of this aerodynamic regime. In the present work, it is proposed to study the unsteady aerodynamic analysis of 2D airfoil using CFD software and Xfoil panel code method. The various steps involved in this work are geometric modelling using CATIA V5R17, meshing using ICEM CFD, and solution and postprocessing through FLUENT. The finite control volume analysis and Xfoil panel code method has been carried out to predict aerodynamic characteristics such as lift coefficients, drag coefficients, moment coefficients, pressure coefficients, and flow visualization. The lift and drag coefficients were compared for all the simulations with experimental results. It was observed that for the 2D airfoil, lift and drag both compared well for the midrange angle of attack from −10 to 15 degree AOA.

A preliminary classification of coastal sand dunes of KwaZulu-Natal

Jackson, D.W.T.., Cooper, J.A.G., Green, A.N., 2014. A preliminary classification of sand dunes of the KwaZulu-Natal coast. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 718–722, ISSN 0749-0208.The 550 km-long KwaZulu-Natal coast broadly divides into a bedrock-framed southern section and northern coastal plain section, each of approximately equal length. Seven types of coastal dune are identified on this coast: estuary barrier dunes; mainland beach foredunes; prograded beachridge dunes; headland bypass dunes; transverse dune fields; parabolic/migrating dunefield; and climbing dunes. The development and distribution of the various dune forms is more strongly controlled by the geological setting, than the aerodynamic regime.

The Natural Physical Cavity Energy Regime of Double-Skin Facade

The subject of the paper is natural physical cavity of double-skin corridor type facade with year-round open circuit and effective height equal to height of one floor. Goal of the paper is quantification of thermal, aerodynamic and energy regime of this natural physical cavity. Methodology of the paper is long term in-situ experimental research (that means under the load of real conditions of the exterior climate on the building), confrontation of the theory and experiment and scientific polemic to new knowledge. Description of experimentally investigated double-skin facade. Description of the experiment in-situ (basic data, monitored physical parameters, measuring technology). Presentation of research results. New knowledges about regime of natural physical cavity of double-skin facade under windless climate conditions and under wind climate conditions. New knowledges lead us to the most important piece of knowledge about the real maximal increase of the temperatures in the cavity, which is the decisive factor for building ecology (natural ventilation from the cavity) and equally for energy (energy consumption) of a building with double-skin facade.

Aerodynamic Mode of Double-Skin Transparent Façade with Narrow Physical Cavity and its Influence on Indoor Environment in the Summer Season

Tall slab-shaped building of north-south orientation. Narrow-cavity double skin transparent façade. South (S) external wall with application of double-skin transparent façade. Aerodynamic regime of narrow-cavity double skin transparent façade in summer. The total aerodynamic resistance of natural physical cavity and its relationship to the convection air lift force. Air stagnation in the cavity as the physical defect of the double-skin façade. Aerodynamics of the double-skin transparent façade as a conditional factor of the thermal discomfort of indoor climate in the building.

Spatial patterns of aeolian sediment deposition in vegetation canopies: Observations from wind tunnel experiments using colored sand

In environments affected by wind erosion, plants act as traps for aeolian sediment, which leads to a small-scale mosaic of depositional and erosional sediment transport regimes. This wind tunnel study used colored sand to visualize spatial patterns of sediment redistribution within grass canopies. Wind tunnel experiments were performed with high-, medium- and low-density canopies of Lolium perenne, corresponding to vegetation covers of 47%, 16% and 4%, respectively. In the low and medium-density canopies, the wake areas downstream of the tussocks were the primary locations of sediment deposition. In the medium-density canopy, these wedge-shaped wake deposits overlapped with the adjacent downstream tussocks, while in the low-density canopy they did not, indicating that these vegetation densities respectively represented wake-interference and isolated roughness flow. In the high-density canopy, very few sand grains were entrained by the wind, and were mostly deposited within the disturbed zones surrounding the tussocks. The deposited grains were evenly distributed around the tussocks in the high-density canopy without pronounced accumulations on their upstream, downstream or lateral sides. We interpret the high-density canopy as a skimming flow aerodynamic regime. The fraction of the sand surface which was exposed to erosion was substantially smaller than the area not covered by grasses. It accounted for 67–78% of the non-covered surface in the low-density canopy, and for 44–77% of the surface in the medium-density canopy. This finding indicates that wind erosion models overestimate the sediment source area if they assume the erodible area is the entire exposed surface not covered by roughness elements.

Parameter Identification for Unsteady Aerodynamic Systems by the Modulating Function Technique

The longitudinal dynamics of aircraft is extended into the unsteady aerodynamic regime by the inclusion of indiciai functions. A ‘grey box’ identification problem is formulated with a least squares algorithm for the modulating function technique and Schroeder-phased multisinusoidal input signals are used to improve the noise properties of the algorithm.

Patients, devices and formulations

The success of inhalation therapy depends on exploiting the complex interaction between the patient, the inhalation device and the formulation it contains. For pressurised metered dose inhalers, good respirability demands stable particulate dispersions in approved propellents, valves which meter accurately and patients trained in suitable breathing manoeuvres. The comparable requirements for a powder inhaler are friable powder aggregates contained in a device capable of generating a turbulent aerodynamic regime at a low inspiratory resistance.

Performance of a Compressor Cascade Configuration With Supersonic Entrance Flow—A Review and Comparison of Experiments in Three Installations

A cascade geometry derived from a research program on high-throughflow, transonic, axial-flow compressors was tested with similar supersonic entrance flow conditions in three linear cascade test facilities. The airfoil section used was representative of advanced rotor-blade, tip-region profiles designed to operate at inlet relative Mach numbers of 1.4 to 1.8. Objectives in the experiments were to study the reproducibility of test conditions and measured performance in facilities that are considered to be “state-of-the-art,” and to generate data sets that could be used as test cases or “benchmark” results to validate computational methods for turbomachine application. It was recognized from the beginning of the project that the aerodynamic regime involved represents a very difficult combination of problems in both experimentation and computation. This difficulty was certainly encountered; the experimental problems are fully discussed in this paper and the companion papers originating in two of the test groups. An excellent series of data sets has been obtained, and our confidence in the results is supported by the exchange of information and personnel that occurred during all phases of the experiments. The results presented here and in the forthcoming AGARD Propulsion and Energetics Panel “test case” compendium should serve as a standard for evaluating current and future computational efforts.

Influence of air pressure variations on the aerodynamic regime of the worked-out area

Influence of air pressure variations on the aerodynamic regime of the worked-out area

Preliminary Control System Using Preferred Feedback States

Theme T objectives of this paper are twofold: first, to present the fin position 6 and body rate 0 feedback shaping transfer functions that equate a conventional fin feedback autopilot to a autopilot that replaces fin feedback with body angular acceleration 6 as a feedback signal. The word reference is used because there are no practical angular accelerometer sensors available for measuring body angular accelerations, and also, for analysis reasons, the angular acceleration loop is assumed to be free of the tolerance problem that is inherent in matching M6 in the feedback path with M5 in the forward path. The second objective is to demonstrate the practical application of this control scheme by analysis and examples with the end view being to facilitate rigid-body autopilot design work and to maximize the controllable aerodynamic regime of vehicles that are subject to large Ma.