The accuracy of existing methods for estimating the drag based on experimental flow field measurements were assessed for two-dimensional bodies. The effects of control volume boundary placement and inherent simplifying assumptions were also investigated. Wind tunnel experiments were performed on a circular cylinder operating at a Reynolds number of 8,000 and 20,000, and on a NACA 0018 airfoil operating at a chord Reynolds number of 100,000 for three angles of attack (α), specifically, 5◦, 10◦, and 15◦. The circular cylinder experiments fall within the the shear layer transition flow regime. Airfoil investigations span both types of flow development common to low Reynolds number airfoil operation. For α = 5◦ and 10◦, a separation bubble forms on the upper surface of the airfoil, while, for α = 15◦, the flow separates without reattaching, resulting in a stalled airfoil. Wake velocity and pressure measurements were performed at several downstream locations to investigate the impact of control volume boundary placement. Wake profiles were measured between 3 and 40 diameters downstream from the circular cylinder axis and between 1 and 4.5 chord lengths from the trailing edge of the airfoil. In addition to wake profiles, the outer flow velocity variation was quantified to investigate the appropriate location to measure freestream flow characteristics in a test section with streamwise-varying outer flow conditions. The results show that drag estimates are strongly dependent on the streamwise position of the measured wake profile for all methods investigated. Drag estimates improved, and streamwise variation decreased, with increasing streamwise position of the flow measurements. For the pressure based method examined, wake measurements should be taken at least 10 times the projected model height downstream of the model. In the case of the circular cylinder, this is equivalent to 10 diameters and, for the airfoil investigated, it is approximately 1 chord length from the trailing edge. For the methods relying on velocity measurements, acceptable estimates of drag were possible when based on measurements taken at least 30 projected heights downstream, i.e., 30 diameters for the circular cylinder and 3 chord lengths for the airfoil model investigated. The findings highlight the importance of providing a detailed description of the methodology and experimental implementation for drag estimates based on flow field measurements. Finally the study offers guidelines for implementing momentum integral based drag calculations in future investigations.

Psykopati är en personlighetsstörning där specifika beteendemönsteringår. Man kan hitta psykopatiska drag hos barn och ungdomar. Detfinns begränsat med forskning gällande ungdomar med psykopatiskadrag och okänslighet för bestraffning, samt hur föräldrabeteendenpåverkas. Syftet med denna studie är att undersöka om ungdomarsokänslighet för bestraffning medierar länken mellan psykopatiskadrag och föräldrabeteenden. Studien är gjord på tidigare insamladdata från en medelstor stad i Sverige. Sammanlagt deltog 968 flickoroch pojkar, samt svarade deras föräldrar på enkäter. Resultatetvisade att ungdomars okänslighet för bestraffning delvis medierarlänken mellan ungdomars psykopatiska drag och föräldrabeteenden.Dock visade fynden olika resultat för olika föräldrabeteenden. / Psychopathy is a personality disorder where specific patterns ofbehavior are included. It is possible to find psychopathic traits amongchildren and adolescents. There is limited research concerningadolescents with psychopathic traits and insensitivity to punishment,also how the parenting behaviors are affected. The purpose of thisstudy is to research if adolescents’ insensitivity to punishmentmediates the link between psychopathic traits and parenting behaviors.The study is conducted by using previously collected data from anaverage sized city in Sweden. There were 968 participants, where bothgirls and boys and their parents filled out questionnaires. The resultshowed that adolescents’ insensitivity to punishment partly mediatesthe link between youth’s psychopathic traits and parenting behaviors.However the findings showed different paths for different parentingbehaviors.

In this thesis study, air bubble motion in counter-current water flow conditions in a vertical pipe is investigated experimentally. For this purpose, a test set-up was designed and constructed. Images of motions of single bubbles, having different diameters in the range of 3.0-4.8 mm, generated by specially designed bubble injectors were recorded by using a monochrome camera, an image capture card and a PC. Recorded video images were processed to obtain the necessary data for the The purpose of the study is to determine variation as a function of the equivalent bubble diameter, water flow velocity and related dimensionless numbers / Reynolds, Re / E&ouml / tv&ouml / s, Eo / and Weber, We, and is to investigate the bubble shapes and bubble travel paths. Bubble behaviour was investigated at six different counter-current water flow velocities (6.5 cm/s, 7.9 cm/s, 10.5 cm/s, 12.9 cm/s, 15.4 cm/s, and 18.2 cm/s) in addition to stagnant water condition which is taken as the reference case. The direction of the bubble motion is upwards and the direction of the water flow is downwards (i.e. counter-current). Distilled water was used in the experiments. The results of this thesis study for the stagnant water condition have shown good consistency with the previous theoretical and experimental studies found in the literature. For the studied range of bubble diameters, it is observed that the bubble average relative velocity for a certain bubble diameter is less under counter-current water flow conditions than that under stagnant water condition and the drag coefficient values for a certain bubble diameter is higher under counter-current water flow conditions than those under stagnant water condition.

Since the discovery of the drag reduction effects of even small amount of macromolecules in solutions in turbulent pipe flows, there have been many experimental and theoretical studies in order to understand mechanisms behind this phenomenon. Theories have been proposed based on the observations on the change in the characteristics of the turbulent flow near the pipe wall where friction of the momentum transfer between the flow and the conduit takes place. In this study drag reduction in fully developed turbulent pipe flow with four concentrations (200 to 500 wppm) of low molecular weight Sodium Carboxymethylcellulose (CMC) in aqueous solutions was investigated experimentally. Drag reduction was determined by pressure drop measurements. In order to observe the impact of the presence of CMC on the flow, Ultrasound Doppler Velocimetry (UDV) was employed to monitor the instantaneous velocity distributions. UDV is a non-invasive technique allowing one to obtain quick velocity profiles. Experimental measurements were used to calculate Fanning friction factor and radial distributions of the axial time-averaged velocity, velocity fluctuation (turbulent intensity) and eddy viscosity. The drag reduction level was determined through the Fanning friction factor versus Reynolds number data. Velocity data could be obtained as close as 3 mm to the wall by UDV. Two impacts of increasing CMC concentration on the flow field, hence pressure drop, were observed. The first effect was the decrease of the mean velocity gradient especially near the wall with increasing polymer amount which in turn gave rise to lower friction factor or pressure drop. In addition smaller eddy viscosities were obtained in the flow. The second impact of the polymer addition was on the velocity fluctuation or turbulent intensity variation along the radial distribution. An increasing trend in turbulence intensity in the turbulent core with polymer addition was observed. This was in agreement with the earlier studies in which similar turbulence behavior was observed in addition to the suppression of the turbulent intensities near the wall

In this Thesis study, aerodynamic interactions of vehicle models in close following and passing situations were investigated expeimentally. Effect of the inter-vehicle spacing and lateral distance on drag coefficients of two close-following vehicles were observed. Two different types of vehicle models were used in order to investigate the shape effect on aerodynamic vehicle interactions. Drag froces and surface pressures of the models at each situation were measured. Two different blockage correction methods on the basis of drag coefficient results were applied. Linear increments of drag coefficients were observed on leading and trailing MIRA models. Beacuse of their blunter shapes and sharp edges, the leading and trailing Ahmed Body models feel the presence of aerodynamic interactions substantially. The most important reduction in drag force occurs at the least vehicle spacing for both vehicle types. In the passing situations, it was observed that drag coefficients of MIRA models did not change considerably. However, big amount of changes were observed at all positions for Ahmed Body. Maximum values of drag coefficients were reached when the models were at side by side position for both vehicle types. In conclusion, it is possible to obtain more drag reductions with more numbers of vehicles in close-following. the lower drag coefficients in close-following operations caues to increase fuel savings and to reduce air pollution.

Classical approaches to evaluate the stability of large woody debris (LWD) introduced in streams for habitat restoration or flood management purposes are usually based on inappropriate assumptions and hydraulic equations. Results suggest that the physics of small cylindrical elements located in large channels cannot be transferred to the case of a large roughness elements placed in small channels. The introduction of LWD in a small channel can generate a significant modification of the upstream hydraulic conditions. This modification has direct implications on the stability of the LWD. Experiments were performed in a controlled environment: a small stream section was represented by a low roughness rectangular flume and LWD were modeled with smooth PVC cylinders. Direct force measurements were performed with a load cell and results were used to identify an equation that evaluates the drag force acting on a large cylindrical element place in a rectangular channel. This equation does not depend on a drag coefficient. Water depths were also measured during the experiments and results were used to develop an approach that evaluates the upstream hydraulic impacts of a large cylinder introduced in a rectangular channel. The effect of the variation of the unit discharge (discharge per unit of width), cylinder size, cylinder elevation from the channel bed, and downstream hydraulic conditions, could be related to the upstream hydraulic conditions with relative success. Dimensionless parameters were developed to increase the versatility of the approach. The application of this approach to field cases is expected to require adjustments, mainly because of the roughness of natural environments differs from the smoothness of the controlled environment described in this work.

CD-ROM containing source codes of the numerical scheme (appendix A) is attached to back cover. / Includes bibliographical references (leaves 459-472). / System requirements for accompanying CD-ROM: Macintosh or IBM compatible computer. Other requirements: Adobe Acrobat Reader. / xxxvi, 473 leaves ; ill. ; 30 cm. + 1 computer optical disk (4 3/4 in.) / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A numerical scheme, based on discrete-vortex and surface-vorticity boundary-integral methods, has been developed for stimulating time dependent, two-dimensional, viscous flow over arbitary arrays of solid bodies of arbitary cross-section / Thesis (Ph.D.)--Adelaide University, Dept. of Mechanical Engineering, 2001

One of the major challenges of scramjet propulsion remains the generation of sufficient thrust to overcome the large drag of hypersonic vehicles. Since the viscous drag constitutes a large portion of the overall drag, its mitigation offers potential for performance improvement. Viscous drag is generated on all wetted surfaces of the vehicle but is largest in the scramjet combustion chamber, where the fluid not only has a high flow speed, but also a high density. Reduction of the skin friction drag in the combustor hence promises large improvements to the efficiency of the propulsive system. Stalker (2005) proposed a novel approach to skin friction reduction that is based on the combustion of hydrogen within the turbulent boundary layer of supersonic or hypersonic flow. An extension to the theory of van Driest II was developed that suggests that the effectiveness of this method is significantly superior to that of film cooling without combustion effects. In essence, the combustion heat release reduces the velocity gradient at the wall and the density in the boundary layer so that the momentum transfer to the wall is decreased. This work investigates the applicability of this skin friction reduction method to scramjet combustors that would operate at flight Mach numbers between 8 and 13 at altitudes between 34 and 39 km. The corresponding combustor Mach number is approximately 4.5 and the total enthalpies are between 3.6 and 7.8 MJ/kg. Experiments that directly measured the skin friction drag on the internal scramjet combustor surface were conducted in the T4 Stalker tube at The University of Queensland. A constant area, axisymmetric combustor was tested with a matching constant area, axisymmetric inlet that did not compress the oncoming flow. Therefore, the experiments were of a quasi-direct-connect nature where the inlet was used to condition the wall layer of the flow that enters the combustion chamber. The start of the combustor was formed by a step at the end of the inlet which contained an annular slot for the injection of the gaseous hydrogen fuel. Fuel was injected tangentially to the main stream flow into the circular combustor as a uniform layer underneath the established boundary layer from this annular slot. Combustion was monitored via the measurement of the axial pressure distribution in the combustor and viscous forces on the combustor were measured with a stress wave force balance. Two different inlet lengths were tested to assess the effect of the boundary layer state and thickness on the ignition and combustion of the injected hydrogen. The leading edge of the inlet was either sharp or blunt to investigate the effect of the hot gas that is contained in an entropy layer that is generated by a blunt leading edge. Finally, the diameter of the duct was varied to ensure that the experimental data was not subject to duct scaling effects. The effect on skin friction of the combustion of fuel in the boundary layer was assessed directly by measurement as well as analytically with several prediction methods. The experimental data show reductions of skin friction drag of up to 77% when stable combustion was established. A thick, turbulent boundary layer results in ignition for lower enthalpy conditions than a thin, laminar layer. The blunted leading edge configuration creates conditions that results in ignition of the injected fuel at all tested flow enthalpies and when a sharp leading edge configuration does not. Analytical predictions of the skin friction drag are in close agreement with the experimental data for fuel-off, film cooling and boundary layer combustion cases. It is demonstrated that the characteristics of boundary layer combustion do not change when the duct diameter is increased and the hydrogen mass flow rate per unit circumferential length is kept constant.

Thesis(M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.) -- Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.