The unobvious effect of the limiting wetting angle on heat transfer intensity at boiling is shown. The purposeful experiments allow us to develop the mathematical model, which describes properly the results of experiments on determination of the role of limiting wetting angle: sometimes this role is obvious, sometimes it is ambiguous.
Experiments are performed to study the possibility of decreasing the net drag of a flat plate with the use of streamwise-oriented vertical elements mounted normal to the surface in an incompressible equilibrium turbulent boundary layer. The Reynolds number based on the boundary-layer momentum thickness in the section where the vertical elements are placed is 820. It is demonstrated that vertical large eddy breakup elements with the geometry used do not reduce the drag of a flat plate in the major part of the range of Reynolds numbers Reх examined. It is only at extremely low values of Reх that a certain gain in the net drag is reached, as compared with the value for a non-modified flow.
In the present study, we examined, both experimentally and theoretically, the influence of surface permeability on the stability and laminar-turbulent transition of supersonic boundary layer at free-stream Mach number М∞ = 2. A satisfactory agreement was obtained between the data calculated by the linear theory of stability and the data obtained in experiments with natural disturbances performed on models with different porous inserts.
Flow of two high-lift devices is studied on the basis of the solution to two-dimensional Reynolds equations with the Spalart - Allmaras one-equation turbulence model. Computation results are compared with the experiment under the conditions of airfoil flow in the low-speed wind tunnel with open test section. It is shown that such approach is the most correct for this comparison.
Presented below are the results of tests of turbine vanes with vertical rotation axis aimed at determination of their aerodynamic characteristics. Three types of vanes with the profiles in the form of semicylinder, semiellipse, and semiellipse with stabilizing plane have been tested. The last type of vane has been tested with stationary and rotary stabilizing planes.
The dependence of the flow patterns around two prism bodies with square cross sections on the distance between them has been studied. The specific structures arising around two bluff bodies have been obtained and divided into four main types. The thermoanemometer probing in aerodynamic wake of the same two bodies has been performed and resulted in the presented dependence of Strouhal numbers on the relative distance between the investigated prisms.
Presented below is the review of the results of experimental studies of energy characteristics of Darrieus rotor with vertical rotation axis. Influence of main geometry parameters of the rotor on its energy characteristics has been analyzed. It is shown that Darrieus rotor may have the higher level of energy characteristics than the best propeller wind turbines.
A novel approach was proposed to developing a combined algebraic-differential model of turbulent viscosity, which was then used to modify the traditional method for calculating turbulent boundary layers on bodies of revolution immersed in an incompressible flow. Ample experimental data were invoked to test the developed model through prediction of features inherent in turbulent boundary layers on the body of revolution in the presence of Large Eddy BreakUp (LEBU) devices installed in the vicinity of the streamlined surface. Within the developed approach, we showed it possible to calculate the evolution of local governing characteristics of turbulent flow in a broad range of LEBU parameters.
The PIV technique was used to measure the instantaneous vector fields of flow velocity and vorticity behind a thin cross-flow rib installed in a channel with laminar, transient, or turbulent flow. The data were treated statistically to determine the fields of mean longitudinal flow velocity and the correlations of pulsating velocity components 〈u′v′〉 and 〈u′u′〉. Some features of the flow structure developing under conditions of laminar-turbulent transition behind the rib have been revealed.
Viscous gas flow in the domain with a cubic package of spheres is considered. The problem formulation and the solution method are briefly presented. The integral parameters are presented, and the flow character is identified.
