Download or read book A Quantitative Investigation of Surface Roughness Effects on Airfoil Boundary Layer Transition Using Infrared Thermography written by Todd Daniel Beeby and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation of the impact of subcritical leading edge distributed roughness elements on airfoil boundary layer transition location has been undertaken using infrared thermography. In particular, a quantitative approach to boundary layer transition location detection using a differential energy balance method was implemented using a heating pad to produce constant heat flux. This was performed on a S809 airfoil model at Re[subscript]c = 0.75 and 1.0 x 106, using roughness elements of height k/c = 3.75, 4.25 and 5.00 x 10−4, pattern densities of 2 to 10 %, and roughness locations of 1 to 6 % chord. Turbulator tape of height k/c = 6.67 x 10−4 was also examined. Results indicate significant impact on transition for all roughness cases, and a more pronounced influence of roughness density as compared to roughness element height. The phenomenon of early laminar bubble collapse was also found to occur for some roughness configurations. The quantitative method used was found to be an effective means for automated transition location determination.
Download or read book Effects of Specific Types of Surface Roughness on Boundary layer Transition written by Laurence K. Loftin and published by . This book was released on 1946 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Summary: Tests were conducted with two typical low-drag airfoils of 90-inch chord to determine the effects of surface projections, grooves, and sanding scratches on boundary-layer transition. The Reynolds number at which a spanwise row of cylindrical projections would cause premature transition was determined for a range of Reynolds number from approximately 3 x 106 to 10 x 106. Data were obtained for projections of various sizes and chordwise locations on both low-drag airfoils. The results were analyzed on the assumption that the critical airfoil Reynolds number for a given projection was a function only of the local-flow conditions around the projection. This assumption neglected possible effects of tunnel turbulence, pressure gradient, boundary-layer Reynolds number, and the original extent of the laminar flow. The data correlated on the basis of this assumption within a range of critical airfoil Reynolds number of ±0.5 x 106 and within a range of projection height of ±0.002 inch. The tests of surface grooves and sanding scratches indicated that, for the range of Reynolds number investigated, the laminar boundary layer was much less sensitive to surface grooves and sanding scratches than to projections above the surface.
Download or read book An Extension of the Investigation of the Effects of Heat Transfer on Boundary layer Transition on a Parabolic Body of Revolution NACA RM 10 at a Mach Number of 1 61 written by K. R. Czarnecki and published by . This book was released on 1954 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results indicate that the trend found previously of an increase in boundary-layer transition Reynolds number with increase in model cooling continued to higher Reynolds numbers. The highest transition Reynolds number obtained with cooling was 28,500,000. At this Reynolds number, the classical Tollmien-Schlichting wave type of boundary-layer number, the instability was apparently overshadowed by surface roughness effects. The results indicated that, when transition was fixed by surface irregularities or airstream flow disturbances, cooling was not effective in obtaining laminar flow behind the irregularity or disturbances.
Download or read book Preliminary Investigation of the Effects of Heat Transfer on Boundary layer Transition on a Parabolic Body of Revolution NACA RM 10 at a Mach Number of 1 61 written by K. R. Czarnecki and published by . This book was released on 1952 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental investigation of the effects of surface roughness on compressible turbulent boundary layer skin friction and heat transfer written by Frank Levi Young and published by . This book was released on 1965 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1987 with total page 1126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book Use of a Liquid crystal Heater element Composite for Quantitative High resolution Heat Transfer Coefficients on a Turbine Airfoil Including Turbulence and Surface Roughness Effects written by Steven A. Hippensteele and published by . This book was released on 1986 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigations of Surface Roughness Effects on Turbulent Flow and Heat Transfer written by and published by . This book was released on 1990 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of this research program was to investigate the effects of surface roughness on turbulent boundary layer heat transfer by obtaining accurate, comprehensive, quality heat transfer data for zero pressure gradient incompressible air flow over constant temperature test surfaces with well-defined surface roughness geometries. Knowledge gained from the experimental investigation was used to improve and extend the roughness energy transport model used in the discrete element prediction method, thus enhancing and expanding the capability to predict the effects of surface roughness on turbulent flow and heat transfer. Fluid dynamics and heat transfer data for turbulent boundary layer flow over a smooth and five rough surfaces were taken in the Turbulent Heat Transfer Test Facility (THTTF) for x-Reynolds numbers ranging up to 10,000,000. The smooth wall data was used for qualification of the THTTF and provided base line data for comparison with the data from rough surfaces.
Download or read book Preliminary Results from a Free flight Investigation of Boundary layer Transition and Heat Transfer on a Highly Polished 8 inch diameter Hemisphere cylinder at Mach Numbers Up to 3 and Reynolds Numbers Based on a Length of 1 Foot Up to 17 7 X 106 written by James R. Hall and published by . This book was released on 1957 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Study of Surface Roughness Effects on Turbulent Boundary Layer Flow and Heat Transfer written by Hugh W. Coleman and published by . This book was released on 1987 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the first year of this program the calibration and qualification of the turbulent heat transfer test apparatus were completed for heat transfer measurements. The heat transfer data taken for zero pressure gradient, constant wall temperature, incompressible flow over a smooth wall agree with standard, accepted data sets for such conditions within the scatter of the standard data.
Download or read book Experiments on the Effects of Air Jets and Surface Roughness on the Boundary Layer Near the Nose of an N A C A 64A006 Aerofoil written by D. G. Hurley and published by . This book was released on 1953 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigations on Roughness Initiated Instability and Transition in Airfoil Boundary Layers written by Benjamin Plogmann and published by . This book was released on 2015 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Study of the Effects of Roughness and Curvature on Heat Transfer in Turbulent Boundary Layers written by Sylvia Huebbe-Walker and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Study of the Localized Effects of Dimple Roughness on Heat Transfer in Turbulent Boundary Layer Flow written by Mark E. Kithcart and published by . This book was released on 2001 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat transfer enhancement has been an area of significant interest within the thermal science discipline for many years. In particular, the use of surface roughness has been found to be an effective method of achieving this goal under convective conditions. More recently however, ways have been sought which would maximize heat transfer without the usual augmentation (created by certain types of roughness geometries) in pressure drop or friction, a consequence which results in lower overall operational efficiency. Based on data obtained by the author and others, surfaces roughened with dimple elements have shown promise in that heat flux is enhanced while drag augmentation is low relative to smooth plate values. The aforementioned studies generated valuable data, however the physical mechanisms which allow for significant heat transfer enhancement along with modest drag increase have not been accounted for (in other words, understanding the physics would allow for manipulation of certain parameters which could result in even greater efficiencies). To this end, the local effects of dimple roughness elements on turbulent boundary layer flow were studied numerically using the FLUENT CFD software package. In addition validating experiments were carried out concurrent with the numerical investigation, and data from another experiment were used for comparison. In the simulations, single dimple elements were examined in three configurations: Shallow, hemispherical and deep, where these designations refer to the ratio of element diameter to depth. Also, two closely-spaced dimples in tandem were modeled. The results of the initial numerical simulation on a hemispherical single dimple indicate that heat transfer enhancement is a consequence of a complex flow-field created by impinging flow on the rear edge of the dimple. The multiple dimple simulation was done in order to assess the effect of one dimple on another. This study showed that the dimples exhibit the same flow-field characteristics displayed by the single element, however (and most importantly) the elements have no discernable effect on one another. Further investigation involving the single dimples of various depths indicate that, in accordance with experimental results found in the literature, hemispherical dimple elements generate higher levels of heat transfer than the shallow and deep configurations and thus should be considered as the optimal geometry for heat transfer applications.
Download or read book An Investigation of Surface Roughness Shape Effects on Turbulent Flow and Heat Transfer written by James Whitley Garner and published by . This book was released on 1990 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Preliminary Investigation of the Effects of Heat Transfer on Boundary layer Transition on a Parabolic Body of Revolution NACA RM 10 at a Mach Number of 1 61 written by K. R. Czarnecki and published by . This book was released on 1954 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: A preliminary investigation has been made of the effects of heat transfer on boundary-layer transition on a body of revolution at a Mach number of 1.61 and over a Reynolds number range of 7,000,000 to 20,000,000, based on body length. The body had a parabolic-arc profile, blunt-base, and a fineness ratio of 12.2 (NACA RM-10). The results indicated that, by cooling the model an average of about 50 degrees F, the Reynolds number for which laminar boundary-layer flow could be maintained over the entire length of the body was increased from the value of 11,500,000 without cooling to over 20,000,000, the limit of the present tests. Heatig the model an average of about 12 degrees F on the other hand decreased the transition Reynolds number from 11,500,000 to about 8,000,000. These effects of heat transfer on transition were considerably larger than previously found in similar investigations in other wind tunnels. It appears that, if the boundary-layer transition Reynolds number for zero heat transfer is large, as in the present experiments, then the sensitivity of transition to heating or cooling is high; if the zero-heat-transfer transition Reynolds number is low, then transition is relatively insensitive to heat-transfer effects.
Download or read book Airfoil Boundary layer Transition Due to Large Isolated 3 D Roughness Elements in a Favorable Pressure Gradient written by Matthew Joseph Cummings and published by . This book was released on 1995 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
