A method for designing three-dimensional configurations with prescribed skin friction

1984 ◽  
Vol 21 (11) ◽  
pp. 924-926 ◽  
Author(s):  
S. G. Lekoudis ◽  
N. L. Sankar ◽  
S. F. Radwan
Keyword(s):  
Skin Friction ◽  
Three Dimensional ◽  
Prescribed Skin Friction

The Behavior of the Casing Boundary Layer With the Presence of Tip Leakage Vortex

2018 ◽  
Author(s):  
Xi Nan ◽  
Feng Lin ◽  
Takehiro Himeno ◽  
Toshinori Watanabe
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Flow Loss ◽  
Produce Flow

Casing boundary layer effectively places a limit on the pressure rise capability achievable by the compressor. The separation of the casing boundary layer not only produce flow loss but also closely related to the compressor rotating stall. The motivation of this paper is to present a viewpoint that the casing boundary layer should be paid attention to in parallel with other flow factors on rotating stall trigger. This paper illustrates the casing boundary layer behavior by displaying its separation phenomena with the presence of tip leakage vortex at different flow conditions. Skin friction lines and the corresponding absolute streamlines are used to demonstrate the three-dimensional flow patterns on and near the casing. The results depict a Saddle, a Node and several tufts of skin friction lines dividing the passage into four zones. The tip leakage vortex is enfolded within one of the zones by the separated flows. All the flows in each blade passage are confined within the passage as long as the compressor is stable. The casing boundary layer of a transonic compressor is also examined in the same way, which results in qualitatively similar zonal flows that enfolds the tip leakage vortex. This research develops a new way to study the casing boundary layer in rotating compressors. The results may provide a first-principle based explanation to stalling mechanisms for compressors that are casing sensitive.

Numerical Simulation for Radiated Flow in Rotating Channel with Homogeneous-Heterogeneous Reactions

2019 ◽  
Vol 44 (4) ◽  
pp. 355-362 ◽  
Author(s):  
Tasawar Hayat ◽  
Ikram Ullah ◽  
Ahmed Alsaedi ◽  
Hamed Alsulami
Keyword(s):  
Skin Friction ◽  
Heat Generation ◽  
Radiation Effects ◽  
Three Dimensional ◽  
Reynold Number ◽  
Heterogeneous Reactions ◽  
Shooting Technique ◽  
Heterogeneous Features ◽  
The Impact ◽  
Rotating Channel

Abstract The present work models MHD three-dimensional flow in a rotating channel. The energy expression is characterized by heat generation/absorption and radiation effects. Homogeneous-heterogeneous features are also accounted for. The obtained non-dimensional systems are numerically computed via the NDSolve based Shooting technique. Graphs are plotted to visualize the impact of various influential variables on velocity, temperature and concentration. In addition, skin friction and the Nusselt number are numerically estimated. Here temperature increases for increasing estimations of heat generation/absorption and radiation parameters. Furthermore, skin friction is reduced in the case of large Reynold number and rotation parameter.

Boundary layer over a blunt body at low incidence with circumferential reversed flow

1975 ◽  
Vol 72 (1) ◽  
pp. 49-65 ◽  
Author(s):  
K. C. Wang
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Blunt Body ◽  
Three Dimensional ◽  
Prolate Spheroid ◽  
Three Dimensions ◽  
General Context ◽  
Reversed Flow ◽  
Low Incidence

This paper investigates the three-dimensional laminar boundary layer over a blunt body (a prolate spheroid) at low incidence and with reversed flow. Results reflecting the general characteristics of such a problem are presented. More significant are the features relating to the circumferential flow reversal. Some of these features confirm our early hypotheses concerning the existence of a reversed region ahead of separation and the role of the zero-cfθ line in the general context of separation in three dimensions. Other features are unexpected, including the distribution of cfμ and the shape of the separation line. Here cfθ and cfμ denote, respectively, the circumferential and meridional components of the skin friction.

Control of Separated Boundary-Layer on Subsonic Airfoil Using Vortex Generator Jet Devices

2006 ◽  
Author(s):  
A. Kourta ◽  
G. Petit ◽  
J. C. Courty ◽  
J. P. Rosenblum
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Leading Edge ◽  
Skin Friction Coefficient ◽  
Synthetic Jets ◽  
High Lift ◽  
Longitudinal Vortices

The control of subsonic high lift induced separation on airfoil may improve the flight envelope of current aircraft or even simplify the complex and heavy high-lift devices on commercial airframes. Until now, synthetic jets have proved a really interesting efficiency to delay or remove even leading-edge located separated areas on high-lift configuration but are not efficient for real scale aircrafts. In case of pressure-like separation (i.e. from trailing-edge), synthetic jets can be replaced by so the called “Vortex Generator Jets” which create strong longitudinal vortices that increase mixing in inner boundary layer and consequently the skin friction coefficient is increased to prevent separation. In this study, numerical simulations were undertaken on a generic three dimensional flat plate in order to quantify the effect of the longitudinal vortices on the natural skin friction coefficient. Both counter and co-rotative devices were tested at different exhaust velocities and distances between each others. Finally co-rotative vortex generators jets were tested on a three dimensional generic airfoil ONERA D. Results show a delay of the separation occurence but this solution does not seem to be as robust as synthetic jets. The study of jets spacing with respect to the efficiency of the devices shows a maximum for a given ratio of spacing to exhaust velocity.

scholarly journals Evaluation of Skin Friction Drag Reduction in the Turbulent Boundary Layer Using Riblets

2019 ◽  
Vol 9 (23) ◽  
pp. 5199
Author(s):  
Hidemi Takahashi ◽  
Hidetoshi Iijima ◽  
Mitsuru Kurita ◽  
Seigo Koga
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Skin Friction ◽  
Three Dimensional ◽  
Hot Wire ◽  
Friction Drag ◽  
Freestream Velocity ◽  
Turbulent Statistics ◽  
Friction Drag Reduction ◽  
Riblet Surface

A unique approach to evaluate the reduction of skin friction drag by riblets was applied to boundary layer profiles measured in wind tunnel experiments. The proposed approach emphasized the turbulent scales based on hot-wire anemometry data obtained at a sampling frequency of 20 kHz in the turbulent boundary layer to evaluate the skin friction drag reduction. Three-dimensional riblet surfaces were fabricated using aviation paint and were applied to a flat-plate model surface. The turbulent statistics, such as the turbulent scales and intensities, in the boundary layer were identified based on the freestream velocity data obtained from the hot-wire anemometry. Those turbulent statistics obtained for the riblet surface were compared to those obtained for a smooth flat plate without riblets. Results indicated that the riblet surface increased the integral scales and decreased the turbulence intensity, which indicated that the turbulent structure became favorable for reducing skin friction drag. The proposed method showed that the current three-dimensional riblet surface reduced skin friction drag by about 2.8% at a chord length of 67% downstream of the model’s leading edge and at a freestream velocity of 41.7 m/s (Mach 0.12). This result is consistent with that obtained by the momentum integration method based on the pitot-rake measurement, which provided a reference dataset of the boundary layer profile.

scholarly journals Darcy–Forchheimer flow of micropolar nanofluid between two plates in the rotating frame with non-uniform heat generation/absorption

2018 ◽  
Vol 10 (10) ◽  
pp. 168781401880885 ◽  
Author(s):  
Arshad Khan ◽  
Zahir Shah ◽  
Saeed Islam ◽  
Sajad Khan ◽  
Waris Khan ◽  
...  
Keyword(s):  
Skin Friction ◽  
Transverse Velocity ◽  
Three Dimensional ◽  
Skin Friction Coefficient ◽  
Porous Space ◽  
Strong Concentration ◽  
Permeable Media ◽  
Micropolar Nanofluid ◽  
Flow Motion ◽  
Forchheimer Flow

This article studies the Darcy–Forchheimer flow of three-dimensional micropolar nanofluid between parallel and horizontal plates in a rotating system. The micropolar nanofluid in permeable media is described by assuming the Darcy–Forchheimer model, where drenching the permeable space obeys the Darcy–Forchheimer expression. The significant influence of Brownian motion and thermophoresis has been taken in the nanofluids model. The thermal radiation impact is taken to be varying in terms of non-uniform absorption/generation for the purpose to see the concentration as well as the temperature modifications between the nanofluid and the surfaces. The leading equations are converted into a system of differential nonlinear equations and then homotopic method is used for solving the modeled equations. The other physical impacts, that is, skin friction, heat flux, and mass flux, have been studied through tables. The impacts of the porosity, rotation, and inertia coefficient analysis have been mainly focused in this research. It is observed that the higher value of Fr decay the velocity profile, while it increases the transverse velocity, and the increase in the porosity parameter [Formula: see text] increases the porous space, which creates resistance in the flow path and reduces the flow motion. Skin friction coefficient is observed to be larger for the strong concentration [Formula: see text], as compared to the case of weak concentration [Formula: see text]. Impact of strong and weak concentrations on Nusselt and Sherwood numbers seems to be similar in a quantitative sense.

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