The effects of scaling a cavity with respect to a fixed incoming boundary layer thickness on its flow dynamics and control was studied experimentally. Three cavity models with constant length-to-depth ratio of 5 and length-to-width ratio of 2 and with corresponding linear dimensions in the ratio 0.5 : 1 : 2 were tested at freestream Mach number 0.71. Additionally, the 0.5 and 1 scale models were tested at freestream Mach number of 0.85. The experiments involved timeaveraged pressure measurements, unsteady pressure measurements, and PIV measurements. Time-averaged pressure measurements made at the floor were used to study the ’flow-type’ of the cavities. Unsteady pressure measurements were used to study the acoustic characteristics of the cavity. The cavity length-to-boundary layer thickness ratios tested were 10, 20 and 40. The Cp distribution on the clean cavities indicated a change in the cavity flowtype with change in the cavity scale. Varying the L/δ from 10 to 40 changed the cavity flow-type from open to transitional. Analysis of the frequency spectra of the cavity revealed an increase in tonal amplitudes and OASPL with increasing L/δ . The PIV measurements indicated that this could be caused by an increase in energy exchange between the freestream and the cavity. The velocity magnitudes inside the cavities were found to increase with increase in L/δ . A comparative study of different passive control methods on the largest cavity showed that leading-edge spoilers were superior in cavity tone suppression. Of these, the effectiveness of a sawtooth spoiler on the three cavities of different scales was tested. The results showed that while the spoiler was effective in eliminating tones and suppression of noise for the smaller cavities, it was unable to eliminate the tones completely for the largest cavity. To find the correct method for scaling the spoilers with the cavity dimensions, different spoiler heights were tested on the three cavities. The results showed that the cavity noise suppression for a given cavity attains saturation level at a particular spoiler height, called the critical spoiler height. An increase in spoiler height beyond the critical spoiler height was found to have no effect on the noise suppression. It is also found that this critical spoiler height can be scaled with the length of the cavity (for given L/D, M and spoiler profile) irrespective of the boundary layer thickness.

No description available.

Flow control has always been an intense research subject with the pursuit of favourable control effects like drag reduction, transition delay, and separation prevention. In practice, these flow control effects are achieved using mechanical actuators such as deflectors, vortex generators, transverse jets and so on. However, such mechanical actuators may face the drag penalty and limitation of actuation response time. In recent years, energy deposition has been suggested as a novel flow control technique in high-speed flow with preferable characteristics like non-intrusive, easy arrangement and high actuation frequency. The motivation of this work is to experimentally explore the flow behaviour after the certain amount of energy is deposited in Mach 5 flow. The energy deposition is implemented using a thermal bump (surface energy deposition) and laser beam focusing (volumetric energy deposition).This work starts with the development of a measurement technique of luminescent paint for the present challenging hypersonic testing environment, which is used for the further energy deposition experiment. The successes of the luminescent paint development is demonstrated both on two-dimensional and axisymmetric models. The luminescent paint shows high spatial resolution and the accuracy comparing to the pressure transducer reading. The surface energy deposition is performed using an embedded heating element (thermal bump) on a flat plate. Qualitative and quantitative measurement techniques are utilised to study the modification to the flow structure and the alteration to the distribution of pressure and heat transfer rate after thermal bump is activated. The results reveal the appearance of induced shock wave and suspicious vortices traces due to the activated thermal bump as reported in other literatures. Re-distribution of surface pressure and heat transfer rate are also found.For the volumetric energy deposition, the laser beam is firstly focused in quiescent air in order to understand the induced flow pattern and the impingement to a solid plate. High-speed schlieren photography is utilised to provide an insight to the dynamic evolution of the induced shock wave propagation and plasma kernel development after laser-induced air breakdown. Then, the laser energy deposition is conducted over a flat plate with the presence of Mach 5 flow. The outward motion of the induced shock wave significantly distorts the boundary layer and changes the surface pressure distribution. The results show the different pattern of boundary distortion when laser beam energy is deposited at different positions downstream of the leading edge of flat plate. The entire induced flow pattern is similar to those induced by a pulsed micro-jet. In spite of the laser pulse width of 4 ns, the entire dynamic process lasts about 100 μs.

This work develops an empirical method for investigation of the flow properties of blood and applies it to a clinically oriented problem. The development focuses on the characterization of the flow properties of a blood sample. According to the theory of continuum mechanics the steady state flow properties of a material are characterized completely by its constitutive (Burchfield, 1972) function which relates the shear stress measured in a rheometer to the shear rate and hematocrit of the sample. Eleven functions derived from various sources were examined for their ability to fit flow data from thirty—one normal individuals, eleven of whom were using oral contraceptives. (The remainder were not using any drugs). A shear rate range of 0.0312 to 124 s⁻¹ was used at hematocrits from 0.29 to 0.55. A non-linear curve fitting procedure allowed an ordering of the functions to be established with respect to their goodness of fit. The function first employed by Walburn and Schneck (1976), T = X₁ exp (X₂ H+X₄ /H²)D[sup 1-X₃] where T = shear stress, D = shear rate, H = hematocrit and X₁ to X₄ are adjustable parameters, was found to be the most successful. This constitutive function was then used to examine data obtained from a population of normal women at various times during the menstrual cycle, as a hemorheological cycle had been reported to occur over this period. The concentrations of several plasma proteins were also determined and plotted over time. No evident cycle of hemorheological properties or protein concentrations was found. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture "Ultrasonic doppler method for bubbly flow measurement" of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki, which was read by Dr. Hiroshige Kikura. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. The presentations were in particular: M. Aritomi, H. Kikura, Y. Suzuki (Tokyo Institute of Technology): Ultrasonic doppler method for bubbly flow measurement V. V. Kontelev, V. I. Melnikov (TU Nishny Novgorod): An ultrasonic mesh sensor for two-phase flow visualisation A. V. Duncev (TU Nishny Novgorod): Waveguide ultrasonic liquid level transducers for power generating equipment H.-M. Prasser, E. Krepper, D. Lucas, J. Zschau (FZR), D. Peters, G. Pietzsch, W. Taubert, M. Trepte (Teletronic Ingenieurbüro GmbH), Fast wire-mesh sensors for gas-liquid flows and decomposition of gas fraction profiles according to bubble size classes D. Scholz, C. Zippe (FZR): Validation of bubble size measurements with wire-mesh sensors by high-speed video observation A. Manera, H. Hartmann, W.J.M. de Kruijf, T.H.J.J. van der Hagen, R.F. Mudde, (TU Delft, IRI): Low-pressure dynamics of a natural-circulation two-phase flow loop H. Schmidt, O. Herbst, W. Kastner, W. Köhler (Siemens AG KWU): Measuring methods for the investigation of the flow phenomena during external pressure vessel cooling of the boiling water reactor SWR1000 A. Traichel, W. Kästner, S. Schefter, V. Schneider, S. Fleischer, T. Gocht, R. Hampel (HTWS Zittau/Görlitz - IPM): Verification of simulation results of mixture level transients and evaporation processes in level measurement systems using needle-shaped probes S. Richter, M. Aritomi (Tokyo Institute of Technology): Methods for studies on bubbly flow characteristics applying a new electrode-mesh tomograph

The major challenge associated with saving energy in the pumping stations of the fluid transportation in the pipeline networks, especially the crude oil transportation for long-distance is drag forces. In other words, this grossly increases the drag form force and friction losses making fluids transport inside pipeline taken a long time to pass, that increases energy consumption and costs. Therefore, the effective solution to overcome these problems is added drag reduction materials (DRMs) with the main fluid using the drag reduction technique (DR). One of the most important drag reduction technique to enhance flow in the pipeline is an active drag reduction using DRMs. Where the DRMs can reduce drag forces in relatively small amounts part per million (ppm), as well as environment friendly. Thereby, the drag reduction enhancement is highly important in terms of fluid transportation in the many industrial applications. An experimental and mathematical study have been performed in the fully development flow to measure fluid characteristics and to evaluate %DR using various DRMs: polymers, surfactants, and nanoparticles in pipeline network. The active drag reduction experiments have been conducted in the rotational disk apparatus (RDA) and in the closed-loop recirculation system (CLRS) using different solutions of DRMs: individual, binary, and triple at different Reynolds numbers (Re) and at different concentrations. The morphological tests have been done employing XDR, TEM and SEM techniques. Mathematical model was presented to validate the experimental results using the statistic softwareV6.2. The results have been displayed with complete explanation, analysis, and conclusions. The results show that the %DR increases with increasing the velocity (Re) and concentration for the most of DRMs solutions. Also, the results confirm that the use of nanoparticle in complex solutions is more effective than using nanoparticle individually within the same work condition. further, the new complex solutions were formed in a manner that can contribute significantly to increase drag reduction performance and enhance shear resistance of the DRMs. Finally, all microscopy techniques confirm the fact that complex solutions were effectively formed and homogenized within the main fluid.

The purpose of this thesis is to investigate the crossflow and off-the-surface velocity traces on a moderately swept wing at transonic Mach numbers. Computational Fluid Dynamics (CFD) was used to generate the data used to visualize the flow field. This was done for angles of attack of 6, 7, 8 and 10 degrees at a Mach number of 0.8. An overview of flow topology and singular point theory is given as a means to describe the flow field and describe the differences between it at various angles of attack. After performing an investigation of the crossflow velocity traces it was verified that the use of a line of separation in the flow topology as an indication for flow separation is a necessary condition. It was also found that the crossflow topology is more sensitive to shock location than to angle of attack. It has been verified that a line of separation, as defined by Tobak and Peake [ref 1], in the crossflow is an indication that separation may be present on the surface of the wing. Furthermore, shocks complicate the crossflow. In all of the cases the crossflow just aft of a shock becomes much more complex than it was before the shock. New singular points appear and interactions between singular points arise. As angle of attack is increased the flow topology changes critically only in the change from 6 to 7 degrees. This is the range in angle of attack in which a sudden shift in the location of the shock occurs, so it may be postulated that for this wing the flow topology is more sensitive to shock location as opposed to angle of attack. Comparing the topology between the 7, 8 and 10 degree cases, supports this hypothesis as the topology is similar before and after the shock for each case. The flow topology for each case before the shock is much different then the topology just aft of the shock. The investigation of off-the surface traces has shown that as angle of attack is increased the area of separated flow not only grows but also becomes more complex. For the 6 degree angle of attack case, the region of separated flow was concentrated near the surface and as one moved off the surface the flow quickly returned to the attached flow direction with no singular points. This was the case for the 7 degree angle of attack case only the flow did not reattach until after one moved approximately 0.25 feet off the surface. As the angle of attack was increased the distance off the surface in which the flow returned to moving in the downstream direction increased. Furthermore, as angle of attacked was increased the number of singular points and their intensity grew. It was also verified that in all of the cases investigated the presence of a line of separation was an indication of separated flow. Moreover, in all but two cases there were two lines of separation. One located along the furthest outboard and inboard area of the separated region. No lines of separation were observed in or around attached flow, thus the lines of separation may not only indicate that separation is present but in fact give a location for the separated region. / Master of Science

This investigation analyzes the effect of vortex wakes on the Lagrangian displacement of particles induced by the passage of an obstacle in a two-dimensional incompressible, inviscid fluid such that the flow is potential and time-independent in a suitable frame of reference. In addition to the trajectories of individual particles, we also study their drift and the corresponding total drift areas in the Föppl and Kirchhoff potential flow models. Our findings, which are obtained numerically and in some regimes are also supported by asymptotic analysis, are compared to the wakeless potential flow which serves as a reference. We show that in the presence of the Föppl vortex wake some of the particles follow more complicated trajectories featuring a second loop. The appearance of an additional stagnation point in the Föppl flow is identified as a source of this effect. It is also demonstrated that, while the total drift area increases with the size of the wake for large vortex strengths, it is actually decreased for small circulation values. On the other hand, the Kirchhoff flow model is shown to have an unbounded total drift area. By providing a systematic account of the wake effects on the drift, the results of this study will allow for more accurate modeling of hydrodynamic stirring. / Thesis / Master of Science (MSc)

<p> The pressure gradients for sphere trains in 1 in. and 2 in. pipes have been measured with water flowing past the stationary spheres at Reynolds numbers (based on pipe diameter) from to 4 - 105 , and sphere/pipe diameter ratios ranging from 0.486 - 0.84. Two dimensionless pressure ratios have been derived so that the experimental results obtained can be generalised to any pipe diameter with the above constraints on Reynolds number and diameter ratio. Drag coefficients have also been calculated from pressure drop measurements for the 0.84 diam. ratio spheres in· 1 in. pipe. These have been compared with McNoun's drag coefficient. </p> <p> The application of the results to predict pressure gradients for sphere trains in any pipe diameter has been illustrated. </p> / Thesis / Master of Engineering (MEngr)

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