But a part of the process is dependant on surface equipment sometimes not very adapted to the case of the polymer. Specifically, rising fuel costs greatly emphasized the usefulness and necessity of developing efficient viscous drag reduction methods. Experimental findings around coherent vortical structures cvs in turbulent boundary layers and methods of controlling them static and dynamic. The lift coefficient and lifttodrag ratio at aoa 14. Pressure or form drag results from variations in the the normal pressure around the object. Drag reduction via largescale opposition flow control in. Center for turbulence research proceedings of the summer. Xfoil which is optimized for boundary layer suction.
We resorted to three different methods for form drag reduction on that body namely. Meeting these objectives has, of course, also a strong positive impact on the environment. Blended wing body bwb boundary layer ingestion bli. The aerodynamic hysteresis resulted in significant variations of lift coefficient, c l, and lifttodrag ratio, ld, for the airfoil at a given angle of attack. Performance of a boundary layer ingesting bli propulsion. Boundarylayerflow along a flat plate with uniform suction. M system for viscous drag reduction caltech thesis. Click download or read online button to viscous drag reduction in boundary layers book pdf for free now. This wall curvature may increase or decrease the intensity of the turbulent mixing depending on the wall curvature and can strongly affect the skin friction and heat. Drag reduction via largescale opposition flow control in a highreynoldsnumber turbulent boundary layer m. Download pdf viscous drag reduction in boundary layers. Drag reduction, riblets, boundary layers, laminar, openfoam. Pdf drag reduction via turbulent boundary layer flow control. This volume authoritatively treats viscous drag reduction in four major categorieslaminar flow control, passive turbulent drag reduction, active turbulent drag reduction, and interactive turbulent drag reduction and presents emerging technologies, such as the use of surfactants, as an alternative to polymers.
Drag reduction of turbulent boundary layers by means of grooved surfaces. Drag reduction of turbulent boundary layers by means of grooved surfaces citation for published version apa. For subsonic flows, reynolds number can have a significant effect on the level of the maximum turbulence stresses, and the location of that maximum in the boundary layer. Aerodynamic drag reduction by rear under body modification results in up to 22. List and explain the assumptions behind the classical equations of fluid dynamics topicsoutline. In the separation regime downstream of a gurney flap, an absolute instability, i. Aircraft system study of boundary layer ingesting propulsion. Drag forces for turbulent boundary layers learning objectives. A brief overview of each area is provided by a recognized authority to highlight both relevant prior work and the importance of the paper to the drag reduction field.
Riblets are one of the methods used to reduce aircraft surface drag 14. The drag breakdown of a civil transport aircraft shows that the skin friction drag and the liftinduced drag. Compliant surfaces and combined methods for marine vessel drag reduction. Several important geometries in fluid dynamics clearly show the effects of a turbulent boundary layer and its effect on the reduction of overall drag. Friction drag reduction of a spatially developing boundary.
Ingesting the boundary layer however, results in a lower inlet total pressure recovery. Supported by the european union 19961999 notes on numerical fluid mechanics and multidisciplinary design stanewsky, egon, delery, j. For over forty years, the subject has fascinated, frustrated and occasionally gratified scientists and engineers searching for methods to delay laminartoturbulence transition, to reduce skinfriction drag in turbulent wallbounded flows, to quell vibrations, and to suppress. Drag reduction by shock and boundary layer control by egon stanewsky, 9783540433170. Pdf turbulent boundary layer control tblc for skinfriction drag reduction is a. Although system studies have shown that 9% 10% fuel savings can be achieved by delaying boundarylayer. It is also shown that a promising avenue for mitigating the risks aerodynamic as well as aeromechanical in boundary layer ingestion is to mix out the flow before it reaches the engine face.
Drag reduction 6 flopam dr drag reduction the shear degradation of the polymer is limited even at very high speed 25 m. As in the roughwall case no smooth boundary layers can develop, the results demonstrate that bubbly drag. Boundary layer concepts henryk kudela contents 1 introduction external. For lower reynolds numbers, the boundary layer is laminar and the streamwise velocity changes uniformly as one moves away from the wall, as shown on the left side of the picture. Drag reduction by shock and boundary layer control. Drag reduction fundamentals virk 1975 aiche journal. Experiments on a circular cylinder show considerable drag. The charge for this study is to focus on turbulent boundarylayer drag reduction, which was identified as necessary for transoceanic transport at high speeds, i.
Skinfriction drag accounts for approximately one half of the total drag for business jets and longhaul transport aircraft washburn 2011. The boundary layer is a very thin layer of air flowing over the surface of an aircraft wing, or airfoil, as well as other surfaces of the aircraft. Evaluate friction forces on objects using the boundary layer approximation in laminar and turbulent flows 2. Evaluation of skin friction drag reduction in the turbulent. At high reynolds number rex, around 109, a factor of six reduction in drag is the maximum reduction possible, corresponding to the maximum. Turbulent boundary layers in subsonic and supersonic flow. Calculation of viscous drag and turbulent boundarylayer. Turbulent drag reduction using threedimensional structured. Drag reduction by leidenfrost vapor layers request pdf. The tests are conducted in a water tunnel and a towing tank. The topics covered are laminar boundary layers, turbulent flows, nonplanar geometries, blowing and suction, polymer additives, and compliant surfaces. Improvements in fuel efficiency have been estimated as high as 30%. The reynoldsaveraged navierstokes simulation is used to deal with a spatially developing boundary layer on a flat plate at a practically high reynolds number.
Viscous drag reduction in boundary layers progress in. Passive techniques which have been extensively investi. Drag reduction is a great challenge but there is certainly room for improvements. The flat plate with a porous material microbubble injecting system and resistancemeasuring system are set up to measure the frictional resistance of the flat plate without and with injected microbubbles. Pdf viscous drag reduction in boundary layers download. Boundary layer mixture model for a microbubble drag. Hybrid and active control of shock wave turbulent boundary layer interaction and perforated plate. Boundary layers and separation applied computational fluid. Boundary layers are caused by diffusion of momentum. As a result, the combined control is found to reduce the global skin friction coefficient by 44.
Viscous drag reduction in boundary layers download viscous drag reduction in boundary layers ebook pdf or read online books in pdf, epub, and mobi format. There are two key considerations in discussing drag. Reducing aerodynamic drag and fuel consumption year 2002 statistics for combination trucks tractortrailers on nations highways 2. The overall goal of the contract was to design a boundary layer ingesting fan with less than a 2% reduction in fan efficiency at cruise and less than a 2% reduction in stall margin relative to a cleaninflow baseline. In recent years, turbulent boundary layer drag reduction has become an important area of fluid dynamics research. Structure, chemistry, solubility, derivatives, and applications. The experimental evidence is emphasized in three sections concerned with the graphical display of established features of the phenomenon, data correlation and analysis, and the physical mechanism of drag reduction. Turbulence, drag reduction, riblets, boundary layers, skin friction. Compliant coating research is one of those areas which experienced its fair share of triumphs and debacles. This work makes advances in the delay of boundary layer transition from laminar to turbulent ow via feedback control. Control of the transitional boundary layer brandt a. The spheres used were made of steel and tungsten carbide fritsch gmbh, germany, having diameters d 0 10, 15, 20, 25, 30 and 40. Boundary layers, separation, and drag advanced fluid. Numerical study on aerodynamic drag reduction of racing.
Drag reduction via turbulent boundary layer flow control. Thus, the wing should be designed to minimize the drag. A schematic of the experimental setup used is shown in figure 2. This volume authoritatively treats viscous drag reduction in four major categorieslaminar flow control, passive turbulent drag reduction, active. Drag reduction in turbulent boundary layer via flow. Drag reduction of turbulent boundary layers by means of.
The lower inlet total pressure recovery results in a lower pressure in. The present report is concerned with an experimentalinvestigation of bothlaminar and turbulent boundarylayerflow along a flat plate with uniform distributed suction. Numerical analysis and optimization of boundary layer. Viscous drag reduction in boundary layers book osti. Drag force on a flat plate due to boundary layer youtube.
A largescale control strategy for drag reduction in turbulent boundary layers wade schoppa and fazle hussain university of houston, houston, texas 772044792 received 21 october 1997. Viscous drag reduction in boundary layers 1990 citeseerx. Boundary layer combustion for viscous drag reduction in. Viscous flow drag reduction progress in astronautics and. Assessment of shock and boundary layer control a summary. Find materials for this course in the pages linked along the left. Biotechnology and bioprocess engineering from the first ullmanns article to recent trends next article in issue.
Pdf bubbly turbulent drag reduction is a boundary layer. As a precursor to the detailed inlet and fan design, a highlevel, tradefactorbased aircraft system study. The new airfoil proved to have good aerodynamic properties with and without suction and showed vast improvements in pro. This reduction is greatest at the point of optimization but spans over a few hundred viscous lengths downstream of the actuator and about 50 viscous lengths in the spanwise and wallnormal directions. Marusic department of mechanical engineering, the university of melbourne, parkville, vic 3010, australia abstract studies over the past decade have shown that largescale co. Study of control devices applied to a transonic shock waveboundary layer interaction. The present volume discusses the development status of stability theory for laminar flow control design, applied aspects of laminarflow technology, transition. Since the riblets have to be in the inner layer sublayer of the boundary layer in order to for the. Drag reduction due to streamlining and boundarylayer. Biotechnology and bioprocess engineering from the first ullmanns article to recent trends. Therefore, one approach towards drag reduction is to stabilize.
The sphere and the 2d cylinder are two classic examples of how a turbulent boundary layer leads to a smaller wake and less overall drag. The proposed project drag reduction via turbulent boundary layer flow control dragy will approach the problem of turbulent drag reduction through the investigation of activepassive flowcontrol techniques to manipulate the drag produced by the flow structures in turbulent boundary layers. In this paper we describe various methods of boundary layer control which can be applied on bluff body like a busto reduce the form drag on it. Boundary layer effects play a very important part in determining the drag for the aircraft. Boundary layer suction is a boundary layer control technique in which an air pump is used to extract the boundary layer at the wing or the inlet of an aircraft. Drag reduction via turbulent boundary layer flow control article pdf available in science china technological sciences 609. Exhaust gas redirecting towards the low pressure zone at the rear of the car is proved to be effective tosome extent, which paves the way of future improvement for future researchers.
The applications include the reduction of drag over streamline bodies e. Viscous drag reduction in boundary layers 1990 by m j walsh, d m bushnell, j n hefner. Bubbly turbulent drag reduction is a boundary layer effect. The surrounding fluid exerts pressure forces and viscous forces. In order to predict the drag on an object correctly, we need to correctly predict the pressure field and the surface shear stress. The boundary mixture model is derived to predict the performance of the microbubble drag reduction technique for a flat plate. At the higher two flow speeds, the bubbles generally remained distinct and skinfriction drag reduction was observed when the bubbly mixture was closer to the plate surface than 300 wall units of the boundarylayer flow without air injection, even when the bubble diameter was.
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