Freestream Flow Research Articles

Effects of upstream wake on vortex-induced vibrations and wake patterns of side-by-side circular cylinders

In this paper, vortex-induced vibrations and wake patterns of two side-by-side circular cylinders in the wake of a stationary upstream cylinder are numerically investigated for a uniform free stream flow at the Reynolds number of 100. The three cylinders are in equilateral triangle arrangements with a center-to-center spacing ratio of 2.0–5.0. The considered mass ratio is 2.0 and the reduced velocity range is 0.5–15.0. The side-by-side cylinders are allowed to vibrate only in the transverse direction. Variations of response amplitudes, frequencies, mean position shifts and wake patterns with the reduced velocity and spacing ratio are investigated using direct numerical simulations. In comparison with the case without an upstream cylinder, amplitudes, frequencies, mean position shifts and hydrodynamic forces of two side-by-side cylinders are significantly impacted by the upstream cylinder wake and the associated wake-vortex-structure interactions. Key observations include (a) vibrations initiated at higher reduced velocities for a small to medium spacing ratio, (b) a wider range of large-amplitude vibrations, (c) a lower-frequency component, (d) appearances of periodic, quasi-periodic, chaotic and asymmetric vibrations, and (e) a hysteresis phenomenon. The asymmetric vibration is characterized by dissimilar vibration amplitudes of the two cylinders whereas the hysteresis is related to a transition of wake patterns when increasing versus decreasing the reduced velocities. Behind two side-by-side circular cylinders, the flip-flopping, anti-phase synchronized, in-phase synchronized, and chaotic patterns are identified.

A flow analysis of hybrid nanoparticles near a solid sphere

In this article, the physical impact on thermal performance of unsteady incompressible hybrid nanofluid Cu−GO/(H2O)−C2H6O2 (50:50 vol%) has been presented by using the implicit finite difference procedure. A rigid circular object is taken for instance at time t=0 , a free stream flow hits the outer surface of the circular object. The fluid crosses the boundary of the circular object at different positions. A highly non-linear complex partial differential system is achieved which is solved numerically. The infiltration of various parameters for instance: nanoparticle shapes (cylinders, bricks and Platelets) and volume fraction parameters on velocity profile, skin friction, temperature profile and Nusselt number are demonstrated qualitatively through illustrations. Outputs specify that: mono nanofluid and hybrid nanofluid created by extending volume fractions causes diminution in the velocity profile. Furthermore, solid hydrogen bonding of hybrid nanofluid reasons a sharp growth in thermal conductivity and, thus, rise in temperature profile is noticed. Moreover, the heat transfer rate and temperature profile has always been influenced by different shape factor, so the cylindrical shape particles lead this category afterwards, bricks and platelets. It is noticed that rise in volume fraction parameters show reduction in velocity profile, but opposite impact is noticed in temperature distribution. Moreover, the thermal performance of hybrid nanoparticles is better than the mono nanoparticles.

Impact of bioconvection on the free stream flow of a pseudoplastic nanofluid past a rotating cone

AbstractIn the current work, the repercussions of Brownian motion and thermophoresis on the three‐dimensional free stream flow of tangent hyperbolic (pseudoplastic) nanofluid past a rotating cone are explored. The tangent hyperbolic model expresses the characteristics of a shear‐thinning nanofluid. Furthermore, oxytactic microorganisms were used as mixers to actively stabilize the nanoparticles. The movement of these microorganisms within the nanofluid gives rise to a major phenomenon termed bioconvection. The flow of nanofluid past a rotating cone finds applications in the field of nuclear reactors, biomedical applications, solar power collectors, steam generators, and so on. The mathematical model is designed using Buongiorno's model that describes the two major slip mechanisms experienced by the nanoparticles moving within a fluid namely thermophoretic force and Brownian motion. The model thus formed is nondimensionalized using the apt similarity transformation. The resulting system is solved by the technique by adapting the shooting method. The velocity, temperature, concentration, and motile density profiles are graphically interpreted for different flow parameters involved in the study. It was observed that thermophoresis reduces concentration and enhances the temperature whereas Brownian motion enhanced both temperature and concentration profiles. Also, the increase in the mixed convection parameter effectively decreased the temperature of the nanofluid.

On the construction of a mode based reduced order model for a moving store

Store separation from aircraft and spacecraft has been a critical issue for the aerospace industry. A potential remedy to reduce resources and to improve turn around time in store separation predictions is the construction of a reduced order model (ROM) that can be utilized for fast and accurate modeling. The objective of this study is to investigate how to construct ROMs for moving bodies and utilize them for both load and subsequently for trajectory predictions of a separating store. To analyze the ROM's capability for load prediction, a preliminary study for modeling distributed pressure loads of pitching and oscillating stores was undertaken. For comparison between modal decomposition and neural networks, the study first used proper orthogonal decomposition (POD), dynamic mode decomposition (DMD), and convolutional neural network (CNN) to reconstruct surface pressures and free stream flow for a pitch up store. Results indicated for pitch up store motion POD would perform most efficiently. The study then used the oscillating store cases to compare two interpolation schemes; namely surface splines and Kriging interpolation. For the oscillating store case, a surrogate ROM-based model was constructed using CFD-simulation data for 12 combinations of reduced frequencies and amplitudes. The resulting ROM-based surrogate model was able to make accurate and fast load predictions for intermediate reduced frequencies and amplitudes. In an attempt to investigate ROM ability to predict store trajectories of intermediate conditions, three cases of store separation at Mach 0.5, 0.8, and 1.2 were considered. It was shown that predictions of trajectories at intermediate Mach numbers can be accomplished using the ROM-based surrogate model constructed from computed store separations at Mach 0.5, 0.8, and 1.2. Results showed a close agreement between CFD and ROM surface loads and as a result trajectory predictions.

Theoretical breakthrough in the dynamics of a jet in a free-stream flow around a corner

For the first time, the laminar jet in a free-stream flow around a corner with/without a moving wall condition (as it assists the flow) is studied theoretically. The corner may contract the streamlines or expand them depending on the angle of inclination. In the context of incompressibility, it is presented a composite non-similar transformation of the Navier-Stokes (N-S) equations in Cartesian space to approximately decipher the nature of the boundary layer flow over the entire physical domain; i.e. 0 ≤ x, y < ∞. The transformed Partial Differential Equations (PDEs) are then solved by an in-house MATLAB code, which employs an implicit algorithm of a tridiagonal form with quasi-linearization technique. For a stationary wall, as the negative angle of the corner meets Falkner-Skan (F-S) limitation and expands beyond, the predictive model starts to show a critical location, which reveals directly the flow separation point. This critical location moves toward the jet origin as the angle of inclination becomes more negative. Here, these locations are extracted as a function of the inclination parameter in order to manifest the suitability of a jet to delay boundary layer separation. A similar scenario also applies to the moving wall case. In this case, it was recorded that a moving wall condition delays separation for a considerable distance. It should be pointed out that up to date, there is no theoretical investigation on this specific flow geometry despite the many associated applications; and the limited available reports on an analogous flow geometry are those from the Computational Fluid Dynamics (CFD) and on a case by case basis. More specifically, the present geometry is quite similar to the flow passing the way down to the trailing edge of an airfoil, with a jet generator mechanism such as Dielectric Barrier Discharge (DBD) plasma actuator to delay flow separation on the backside of the airfoil.Here, by the use of the theoretical non-similarity concept empowered by some recent advancements (see Jafarimoghaddam, 2020 and Jafarimoghaddam, 2021), the fundamental problem of a jet discharged in the lower boundary of a freestream flow over a wedge is successfully solved.This theoretical breakthrough suggests promising avenues for the future design of airfoils with moving parts/flaps as an innovative step forward to enhance maneuverability of the flying objects.

Clap-and-Fling Mechanism in Non-Zero Inflow of a Tailless Two-Winged Flapping-Wing Micro Air Vehicle

The aerodynamic performance of clap-and-fling mechanism in a KU-Beetle—a tailless two-winged flapping-wing micro air vehicle—was investigated for various horizontal free-stream inflows. Three inflow speeds of 0 (hovering), 2.52 m/s and 5.04 m/s corresponding to advance ratios of 0, 0.5 and 1 were considered. The forces and moments for two wing distances of 16 mm (in which the clap-and-fling effect was strong) and 40 mm (in which the clap-and-fling effect was diminished) were computed using commercial software of ANSYS-Fluent 16.2. When the advance ratio increased from 0 to 0.5 and 1, the lift enhancement due to clap in the down-stroke reversal increased from 1.1% to 1.7% and 1.9%, while that in the up-stroke reversal decreased from 2.1% to −0.5% and 1.1%. Thus, in terms of lift enhancement due to clap, the free-stream inflow was more favorable in the down stroke than the up stroke. For all investigated inflow speeds, the clap-and-fling effect augmented the lift and power consumption but reduced the lift-to-power ratio. The total contributions of the fling phases to the enhancements in lift, torque, and power consumption were more than twice those of the clap phases. For the advance ratio from 0 to 0.5 and 1, the enhancement in average lift slightly decreased from 9.9% to 9.4% and 9.1%, respectively, and the augmentation in average power consumption decreased from 12.3% to 10.5% and 9.7%. Meanwhile, the reduction in the average lift-to-power ratio decreased from 2.1% to 1.1% and 0.6%, implying that in terms of aerodynamic efficiency, the free-stream inflow benefits the clap-and-fling effect in the KU-Beetle.

Optimisation of H-Darrieus VAWT Solidity for Energy Extraction in Cooling Tower Exhaust Systems

The technologies surrounding renewable energy have been receiving surmountable attention to producing clean energy and reducing the dependency on depleting fossil fuel sources. In this context, research investigations on vertical axis wind turbines (VAWT) in free stream flow condition has been extensively conducted to improve the energy extraction efficiency from the wind. VAWTs are particularly advantageous in locations not suitable for conventional horizontal axis wind turbines (HAWT). However, the applications of VAWTs are still limited due to their lower performances compared to their counterparts. Furthermore, the wind energy extraction problem is more prominent in urban areas with unpredictable and inadequate wind speed conditions. The present study focuses on an alternative way to harness wind energy from unnatural sources such as cooling tower exhaust systems with the reliable and consistent exhaust air. A three-dimensional numerical study has been conducted to investigate the performance of a 3-bladed H-Darrieus wind turbine (HDWT) using S-1046 airfoils of four different solidities under accelerated wind conditions of a cooling tower. The HDWT model is positioned at the cooling tower outlet, where it rotates using sliding mesh to measure the power output. Shear stress transport (SST) k- turbulence model solver was used to solve the implicit unsteady Reynolds-Averaged Navier-Stokes equations. It is observed that the higher solidity HDWT reached peak power coefficient at a lower tip speed ratio (TSR). In contrast, lower solidity HDWT achieved peak power coefficient at higher TSR. The higher solidity 0.375 and 0.450 produced a maximum power coefficient of 0.233 at TSR of 2.0.

Second law analysis of aerodynamic characteristics with flow temperature variations of simple angle and compound angle full coverage film cooling

The present investigation employs entropy generation to quantify aerodynamic characteristics with flow temperature variations, and the associated second law losses, which are present within a film cooled boundary layer produced by a unique full-coverage compound angle hole configuration. With this arrangement, an alternating sign for the compound angle β is employed from one streamwise row of holes to another, such that compound angle β is +30° in one row of holes, followed by −30° in the next row of holes. Entropy change distributions, entropy generation distributions, and mass-averaged overall exergy destruction from this compound angle arrangement are compared to results from a simple angle arrangement with β = 0°. These quantities are determined from flow field measurements of local flow temperature variations, and local stagnation pressure variations with film cooling. Within the investigation, full-coverage film cooling blowing ratio values range from 2.9 to 6.0, mainstream Reynolds numbers Rems range from 127,000 to 142,000, and effusion flow Reynolds numbers range from about 7000 to approximately 13,000. Distributions of local entropy generation and mass-averaged overall exergy destruction (both relative to freestream flow) are determined using three analysis approaches, which account for local flow temperature variations only, local flow stagnation pressure variations only, and variations of stagnation pressure and local flow temperature together. Similar qualitative trends of local entropy generation for the three different types of data are observed, which mean that temperature and stagnation pressure within the flow experience similar rearrangements by secondary advection and diffusion phenomena for the two film cooling arrangements. From a quantitative perspective, values associated with flow temperature variations only, are consistently larger than values associated with stagnation pressure variations only. Important local variations of local entropy generation are observed for the compound angle arrangement, which are due to skewed and non-symmetric film distributions, along with the associated tilted horseshoe-shaped vortex, which forms around each film coolant concentration.

Experimental investigation of a two-bladed double stage Savonius-akin hydrokinetic turbine at low flow velocity conditions

Savonius-akin hydrokinetic turbine (SAHT) is a promising technology for generating hydropower from an ultra-low head condition with low flow velocity, wherein the kinetic energy of the free-stream flow is converted into mechanical power. The main drawback of SAHT is its lower efficiency. Therefore, the research works in this area is focussed towards improving the performance of such turbine by innovative design and development. The goal of the present work is to investigate the performance of a two-bladed two-stage vertical axis SAHT as a river-stream turbine by changing the gap/clearance between the stages. The stages are mounted on the shaft at 90° out of phase with each other. The gap between stages is varied from 0 to 20 mm in the increment of 5 mm. The experiments are performed under variable load conditions by considering different low flow velocities ranging from 0.4 to 0.6 m/s, commonly found in the perennial rivers. It is found that gap between the stage affects the performance of the SAHT. Based on the experimental results, the optimal loading condition as well as the optimal gap between the stages has been found out. Further, the maximum turbine power and the maximum coefficient of power (Cp) at corresponding TSR are also evaluated for the optimal conditions.

Direct numerical simulation of a stationary spherical particle in fluctuating inflows

Fully resolved direct numerical simulations are conducted to study the effects of fluctuating freestream flow on the drag force and wake characteristics of a stationary spherical particle. Sinusoidal fluctuation around a mean value is adopted as the freestream velocity. The interaction between the particle and fluctuating flow is computed by the direct-forcing immersed boundary method. We principally consider the relative difference between the computed mean drag and the drag law of a uniform flow past the particle and the properties of drag fluctuation in different freestream fluctuation directions. For the influence of streamwise fluctuating inflow, the relative mean drag difference increases with the particle Reynolds number. At small or intermediate particle scale ratios, the relative mean drag difference is very close to zero, indicating that the classical drag law can be used in these cases, while a large particle scale ratio can induce a notable increase in the relative mean drag difference at a large particle Reynolds number and high fluctuation intensity. For the transverse fluctuating inflow, generally, there is an evident increase in the mean drag coefficient when the particle scale ratio is small. Compared with the streamwise fluctuation case, the drag fluctuation intensity is a little smaller with the transverse fluctuating inflow. An explicit empirical drag fluctuation law is obtained by fitting the data for streamwise fluctuating inflow. The wake characteristics are also analyzed, and they are found to be strongly dependent on the direction of inflow fluctuation.

Numerical investigation of double sided plasma vortex generator in separation control

Control of flow separation is a great issue to deal with a moving body to ensure its proper aerodynamic characteristics. To achieve this, various methods including active and passive control are suggested depends upon the flow characteristics and the surface in which control is necessary. To make the better use of both active and passive method of flow control this article proposed a new type of double sided plasma actuator (DSPVG) to overcome the drag penalty of conventional vortex generators (VGs) that commonly used in controlling flow and to use actively control. In this regard, the effectiveness of DSPVG has been numerically and experimentally investigated in a separated flow region of a 20° diffuser of an open type tunnel. DSPVG is placed at the upstream of separation location normal to the surface as like as conventional VG except zero angle with flow direction. Both numerical and experimental results of DSPVG are compared with that of VG and baseline flow and better agreements are found. Moreover, DSPVG has shown better separation suppression ability than conventional VGs due to its dual vortices. It is found that DSPVG significantly delay the separation. A freestream flow of 4 m s−1 is used for experiments and numerical computations.

Numerical Analysis of the Effect of Flexibility on the Propulsive Performance of a Heaving Hydrofoil Undergoing Sinusoidal and Non-Sinusoidal Motions

Abstract Numerical simulations of fluid-structure interaction (FSI) on an elastic foil heaving with constant amplitude in freestream flow are carried out at a low Reynolds number of 20,000. The commercial software STAR-CCM+ is employed to solve the flow field and the large-scale passive deformation of the structure. The results show that introducing a certain degree of flexibility significantly improves the thrust and efficiency of the foil. For each Strouhal number St considered, an optimal flexibility exists for thrust; however, the propulsive efficiency keeps increasing with the increase in flexibility. The visualisation of the vorticity fields elucidates the improvement of the propulsive characteristics by flexibility. Furthermore, the mechanism of thrust generation is discussed by comparing the time-varying thrust coefficient and vortex structure in the wake for both rigid and elastic foils. Finally, in addition to sinusoidal motions, we also consider the effect of non-sinusoidal trajectories defined by flattening parameter S on the propulsive characteristics for both rigid and elastic foils. The non-sinusoidal trajectories defined by S=2 are associated with the maximum thrust, and the highest values of propulsive efficiency are obtained with S=0.5 among the cases considered in this work.

Experimental Study on Insertion Loss of Air Bubble Layer in Freestream Flow

Experimental Study on Insertion Loss of Air Bubble Layer in Freestream Flow

Surface heat flux analysis for opposing jet and combination techniques in the presence of real gas effect

High surface heating is common problem during high speed flights, so it should be properly mitigated for the efficient design of long duration flights. Most of the studies available in the literature are carried out without considering the chemical kinetics of the incoming freestream flow. Hence the current study invokes the thermal non-equilibrium effect (specific heats variation with temperature) and chemical non-equilibrium effect (species continuity equations) on surface heat flux study for the flow over blunt body considering real gas reactions by means of in house developed reacting and perfect gas solvers. Results reveal that surface heat flux reduces with the application of opposing jet and it further reduces for higher pressure ratio of jet. Introduction of cavity reduces the Stanton number but it enhances the drag force on body. Reacting solver gives higher surface heat flux than perfect solver and this difference is larger at low freestream stagnation enthalpy.

Investigating the Level of Fidelity of an Actuator Line Model in Predicting Loads and Deflections of Rotating Blades under Uniform Free-Stream Flow

In this paper, the accuracy of an in-house Actuator Line (AL) model is tested on aeroelastic simulations of a Wind Turbine (WT) rotor and a helicopter Main Rotor (MR) under uniform free-stream flow. For the scope of aeroelastic analyses, the AL model is coupled with an in-house multibody dynamics code in which the blades are modeled as beams. The advantage from the introduction of CFD analysis in rotorcraft aeroelasticity is related to its capability to account in detail for the interaction of the rotor wake with the boundary layer developed on the surrounding bodies. This has proven to be of great importance in order to accurately estimate the aerodynamic forces and thus the corresponding structural loads and deflections of the blades. In wind turbine applications, a good example of the above is the rotor/ground interaction. In helicopter configurations, the interaction of MR with the ground or the fuselage and the interaction of tail rotor with the duct in fenestron configurations are typical examples. Furthermore, CFD aerodynamic analysis is an obvious modeling option in which the above mentioned asset can be combined with the consideration of the mutual interaction of the rotor with the ambient turbulence. A WT rotor operating inside the atmospheric boundary layer under turbulent free-stream flow is such a case. In the paper, AL results are compared against Blade Element Momentum (BEM) and Lifting Line (LL) model results in the case of the WT, whereas LL and measured data are considered in the helicopter cases. Blade loads and deflections are mainly compared as azimuthal variations. In the helicopter MR cases, where comparison is made against experimental data, harmonic analysis of structural loads is shown as well. Overall, AL proves to be as reliable as LL in the canonical cases addressed in this paper in terms of loads and deflections predictions. Therefore, it can be trusted in more complex flow conditions where viscous effects are pronounced.

Investigation of spanwise coherent structures in turbulent backward-facing step flow by time-resolved PIV

We experimentally investigate spanwise coherent structures in the turbulent shear layer downstream of a two-dimensional backward-facing step (BFS). The incoming free-stream flow separates from the backward-facing step edge and then reattaches to the downstream wall surface, resulting in a separated/reattaching shear layer and a recirculation region behind the step. This separated/reattaching shear flow is measured by time-resolved particle image velocimetry (PIV) in one streamwise-vertical plane and three parallel streamwise-spanwise planes, respectively. As a result, the multiple cross-sectional flow diagnosis reveals that the separated shear layer remains two-dimensional from the step edge to approximately the half of the reattachment length. Further downstream, the shear layer begins to flap vertically and it evolves spanwise-oriented structures with alternating high- and low-speed streaks. The near-wall vortex tube beneath the shear layer simultaneously evolves unsteady spanwise variation as well. The unsteady shear layer as well as the vortex tube causes entrainment of the high-momentum fluid from the shear layers downwards into the near-wall vortex tube, and entrainment of the low-momentum fluid upwards in the opposite way. By proper orthogonal decomposition and dynamic mode decomposition, the spanwise coherent structures are characterized as large in size as 2 step heights and they have the same order of frequencies as the vertical pumping and flapping motions, both of which contribute a major part of the turbulent kinetic energy in the shear layer. Further analysis by spatial-temporal cross-correlation function shows that the spanwise coherent structures have influence on the convection velocities of the coherent structures in the latter half of the shear layer.

Shock interaction induced heat flux augmentation in hypersonic flows

This paper gives a summary of dedicated experiments on the shock interaction induced heat flux augmentation, by means of tests carried out in the hypersonic wind tunnel H2K. The first test case is devoted to the shock boundary layer interaction on a flat plate. The interaction impact has been varied by changing the free stream parameters and the position of the shock generator, i.e. shock impingement point on the plate. The heat flux distribution has been determined using surface temperature data measured by an infrared camera. The heat flux data combined with free stream flow parameters allow calculation of the Stanton number evolution. The second test case is a double sphere configuration with a variable axial and lateral distance between the spheres. This allowed measurements of the heat flux augmentation induced by a shock-shock interaction along the complete frontal surface of the second sphere, which was hit by the bow shock of the first sphere. Shock-shock and shock-boundary layer interaction effects are studied by means of experiments on the IXV flight configuration with double control flaps. Depending on the test configuration and flow parameters, shock interaction induced heat flux augmentation factors up to seven have been measured.Graphical abstract

A numerical study to reduce the drag effects in hypersonic flow over the backward facing step

A numerical simulation study of laminar hypersonic cold airflow over the backward-facing step (BFS) is performed at a freestream Knudsen number of 0.00009589 for resolving the flow field. The effects on the wall properties caused by the expansion of the flow and the separation of the boundary layer at the step corner have been investigated. The contributions of pressure and viscosity to the coefficients of lift and drag have been elucidated. It is seen that an increase in step height “nh” from n = 1 to 5 for a freestream flow at Mach 7.6 produces an incremental effect on the CL/CD ratio, whose range is between −1 to 1 for the variations in the step height simulated. The current study concludes that BFS yet remains a geometry that contributes to more drag than lift, however that effect can be minimized by increasing the step height during the design process of hypersonic vehicles for the above-mentioned Mach number.

Flow-induced vibration of a flexible splitter-plate in the wake of a stationary cylinder

The present work is on free-stream flow across a circular cylinder, with a detached flexible-plate. Using a levelset function-based immersed interface method, the effect of Reynolds number Re(75−150), non-dimensional gap G*(0.5−3.5) between the two structures and non-dimensional length L*(0.5−3) of the plate—with constant structural properties and thickness—is numerically studied. The effect of these parameters on the vibration characteristics of the plate along with the accompanying flow structures and engineering parameters are presented. The study demonstrates a correlation between the plate dynamics and the two flow-phenomenon: vortex-formation mode and vortex-interaction mode. Vortex-formation relates to the position of the leading and the trailing edge of the plate relative to the recirculation region behind the cylinder and is classified into three-regimes: pre-vortex formation regime-a, pre-vortex formation regime-b, and post-vortex formation regime, corresponding to smaller, intermediate, and larger plate-amplitudes, respectively. The vortex-interaction mode refers to the nature of interaction between the cylinder and the plate vortices and is classified into two-modes: constructive and destructive interactions, corresponding to larger and smaller amplitudes, respectively. The study shows that the plate oscillates with very large amplitude at larger Re, intermediate G*, and with plate length equal to the cylinder diameter. The flexible plate leads to a large suppression in the hydrodynamic forces and the vortex shedding frequency of the cylinder in the pre-vortex formation regime, with complete suppression in the vortex-shedding for larger plate-length L* at intermediate gap G*. Thus, the present system can be utilized as a plate-based energy harvesting device as well as a vortex-shedding control device.

Hysteresis in Supersonic Flow Past a Plane Cascade of Cylindrical Rods

—The results of numerical simulation of the interaction of supersonic flow with a permeable screen in form of an infinite plane cascade (lattice) of circular cylinders are given. The interaction regime in which the shocks ahead of the cylinders are localized on the scale of the cascade step is considered. The multi-block computational technique in which the viscous boundary layers are resolved by means of local grids using the Navier–Stokes equations, while the effects of inteferrence between the shock-wave structures in supersonic wake are described within the framework of Euler’s equations. The action of shock waves induced by the neighboring elements of lattice to the near-wake region behind the intermediate elements can ambiguously affect the aerodynamic lattice performance as well as generate time-dependent phenomena in the wake. The flow regimes are classified depending on continuous increase and decrease in the free-stream supersonic air flow in the Mach number range from 2.4 to 4.2 with reference to the lattice of the 80% permeability. The sources of the hysteresis behavior of the lattice aerodynamic drag with respect to the Mach number and the mechanisms of the onset of self-oscillating wake flow regimes are discussed.