Using numerical simulation on the basis of Reynolds-averaged Navier–Stokes equations in their closure with the SST turbulence model, a comparison has been conducted of the self-oscillating modes of ...flow around a thick airfoil and a low-aspect-ratio wing with a vortex cell in the presence or absence of slot suction. The inclusion of suction with placement of a ventilator in the off take channel and with jet ejection in the vicinity of the back edge of a two-dimensional airfoil, and also suction into the engine unit on the inner contour of the vortex cell of a thick airfoil stabilize the flow past bodies and improve substantially their aerodynamic characteristics. In a two-dimensional case, the aerodynamic quality increases to 7 and in a three-dimensional variant, it increases to 2.7.
In this paper, we analyze the intensification of the separated flow and heat transfer in single-row, oval-trench dimples with a 45° incline on the heated wall of a narrow channel in the stabilization ...section of a turbulent flow at Re = 10
4
. Anomalously high velocities of the return and secondary flows (on the order of the average mass velocity in the channel), as well as in the entrance part of the dimples, and a multiple excess of the absolute values of negative friction (4.5 times) and heat fluxes (five times) over the friction and Nusselt number on the heated wall of a plane-parallel smooth channel were found. The connection of this phenomenon with the total pressure difference between the close zones of flow deceleration on the windward slope of the dimple and rarefaction at the place of generation of a tornado-like vortex structure was established. The uncertainties in numerical predictions with the use of various grids and semi-empirical turbulence models in the StarCCM+ and VP2/3 packages are discussed.
New tests of software packages and turbulence models for validating the problems of highly intense vortex flows past structured energy-effective surfaces are presented. The idea of the testing is ...based on the discovery of anomalous intensification of separation flows and heat transfer in inclined grooves in plates and channel walls. At the expense of extraordinary pressure differences in the grooves, which are confirmed in experiments, swirl flows with high velocities of return and secondary currents are formed. These velocities are comparable with that of the freestream. Moreover, high-gradient zones with friction and heat removal many times higher (by a factor of from 1.5–2 to 7–9) than the friction and heat removal on a flat wall are formed. By way of illustration, we present the results of testing the VP2/3 software package developed on the basis of original muliblock computational technologies and using intersecting different-in-scale grids. The comparison of the numerical predictions with M.A. Zubin’s experiments confirmed the high static-pressure differences between the deceleration zone on the windward slope of an inclined groove and the negative pressure region at the place of tornado-like flow generation on the spherical entry segment and asserted the applicability of the RANS approach in predicting the characteristics of highly-intense swirled flows.
An analysis of the intensification of a steady-state detached turbulent air flow with Re = 10
4
in a row of oval trench dimples, positioned on the wall of a narrow channel and oriented at an agile of ...45
o
to the incident flow, is given. It is shown that the anomalously high velocities of the reverse and secondary flows at the entrance of such a dimple (of the order of the mean mass velocity of the flow in the channel), as well as the negative friction in this part of the dimple that exceeds in absolute value the friction on the plane wall of the channel by almost five times, are due to the difference between the total pressure in the near zones of stagnation of the air flow at the windward slope of the dimple and the negative pressure at the site of generation of a whirlwind-like vortex structure in the dimple.
The original multiunit computational technologies based on the use of different-scale intersecting grids and implemented in the VP2/3 package are applied to numerically simulate the effect of wind ...shear on a two-dimensional turbulent flow around an energy-efficient high-rise structure. The structure is a circular cylinder in a perforated casing. The throttling effect related to the bypass of air from the braking zone in front of the body to the area of the near-wake behind it stabilizes the flow around the body and reduces its drag. The wind shear is simulated by the vortex street behind the transverse small square-section of a cylinder placed in front of the body. As a test, we consider Igarashi’s experiment on the interaction of a vortex street behind a small-diameter cylinder with a transverse plate in a uniform air flow.
The vortex-induced intensification of the laminar (at Re = 308) flow of transformer oil and heat transfer in a microtube with an in-line package of dimples with a depth of 0.26 of the tube diameter ...is calculated based on the Navier–Stokes equations and the energy equation. The heat-transfer increased by nearly 20 times for eight inclined oval-trench dimples spaced around the circumference and by 13 times for spherical dimples equal in area in comparison with that for a smooth tube; moreover, the relative hydraulic losses grow by approximately 30 and 60%, respectively.
Calculations using multiblock computational technologies and a model of shear-stress transport modified with allowance for the curvature of streamlines in turbulent airflow were performed at a zero ...angle of attack for a semicircular airfoil containing one or two surface vortex cells with slot suction. The results showed evidence of stabilization of a nearly undetached flow and attainment of an extremal lift of
C
y
= 5.2 and a lift-to-drag ratio of
K
= 24 with allowance for energy losses for suction in the vortex cells.
The restructuring of the periodic structure of a turbulent streamline for a semicircular airfoil at a zero angle of attack with a system of slot suction from the circular cavern switched off is ...calculated. Multiblock numerical methods are applied for solution of Reynolds-averaged nonstationary Navier–Stokes equations closed using the modified shear-stress transfer model taking into account flow line curvature. The lifetime of a trapped vortex in a circular cavern is estimated.
Different variants of ventilation of the cab of a truck were investigated by numerical simulation methods. An unsteady viscous gas flow was numerically simulated using the VP2/3 package. In the ...process of numerical simulation of this flow, the Reynolds equations closed with the use of the differential
k
–
ω
model of turbulence in the SST modification of Menter were solved numerically. On the basis of analysis of the fields of the velocity, pressure, and turbulence characteristics of the air flows in the truck cab, obtained as a result of their numerical simulation, the efficiency of ventilation of this cab was estimated.
Recently in building aerodynamics the school of computer simulation of wind influence on the building became urgent. The widespread high building construction plays significant role here. In this ...article the genesis of multiblock calculation methodology for modeling wind influence on the high buildings is presented. The methodology of calculation of wind influence on the high-altitude constructions, based on using multibank overlapping grids of various scales is developed. The methodology is verified on the test problem of a flow around a cube with short circuit with the help of model of shear stress transport. Periodic character of local and integrated wind loadings on a high-altitude building is analyzed. PUBLICATION ABSTRACT
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