Parviz Merati

Global Luminescent Oil-Film Skin-Friction Meter

This paper describes a global luminescent oil-film skin-friction meter that is particularly useful in global skinfriction diagnostics for complex flows. This method is developed based on the relationship between the oil-film thickness and luminescent intensity of an oil film doped with luminescent molecules. The projected thin oil-film equation is given in the image plane, which relates skin friction with the normalized luminescent intensity. A variational formulation with a smoothness constraint on skin friction is given, and the corresponding Euler– Langrage equations are solved to obtain a snapshot solution for a relative skin-friction field. Successive snapshot solutions are superposed to reconstruct a complete relative skin-friction field, and the corresponding absolute field can be further determined by in situ calibration. This method is examined through numerical simulation and experiments.

Aerodynamic disturbances of hot-wire probes and directional sensitivity

Directional responses of hot-wire probes are studied experimentally, and a theory is developed which attributes pitch response to aerodynamic disturbances caused by the probe and yaw response to a combination of aerodynamic disturbances and heat transfer effects. The predicted cooling velocity has the same form as Jorgensens equation, and the pitch coefficient, predicted in terms of the probe geometry, compares favorably with experiments using ideal probes. Comparisons with real probes indicate the limits of validity imposed by hot-wire probe tolerances. The accuracy of Jorgensens equation for combined yaw and pitch has been measured experimentally.

Experimental and Computational Investigation of Flow and Thermal Behavior of a Mechanical Seal

A comparison of a computational model for flow and thermal analysis of a mechanical seal with experimental results is presented. The computational model adequately predicts the flow field in the seal chamber and temperature distribution within the stator of a mechanical seal. This model is used to determine Nusselt numbers on the wetted surfaces of the seal components. The Nusselt numbers can be used to calculate the temperature distribution on the seal face. Flow velocity and pressure, and temperature fields within the seal chamber fluid, stator and rotor are presented. The largest magnitude of the heat flux occurs on the rotor surface near the interface between the rotor and stator. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

Experimental Determination of the Thermal Characteristics of a Mechanical Seal and Its Operating Environment

The thermal distortion of mechanical seal faces has a critical impact on the performance of the seal. Experimental work is discussed which quantifies the thermal characteristics of a mechanical seal and its operating environment. Experimental techniques are employed which measure the seal face torque, thermal gradients, and fluid flow patterns under the normal operating conditions of the seal. The experimental data is used to calculate the heat that is generated at the seal faces and the Nusselt number on the wetted surfaces on the stationary element. The experimentally determined Nusselt numbers are compared to experimental and empirical values that have been presented by other researchers. The effect of the seal geometry on the experimental Nusselt numbers is evaluated.

Flow Investigation Around a V-Sector Ball Valve

Experimental and computational methods were used to study the structure and behavior of the shedded vortices around a V-ball valve. Strouhal frequency for shedded vortices around the valve over a range of operating conditions and flow rates using water as the medium were measured. The information gathered in this study would help to predict at what operating conditions pipe ruptures might occur. A dynamic pressure transducer was used to determine the Strouhal frequency. LDV was used to measure the mean velocity and turbulence magnitudes. FLUENT was used to develop a two dimensional fluid dynamics model. Flow was visualized using high-speed video photography. A dominant large three-dimensional vortex downstream of the valve was detected. The centerline of this vortex is a shadow of the valve lip. A fifth degree polynomial describing the relationship between the Strouhal number and Reynolds number is obtained

EXPERIMENTAL INVESTIGATION OF A TURBULENT FLOW IN THE VICINITY OF AN APPENDAGE MOUNTED ON A FLAT PLATE

Experimental measurements were carried out in an incompressible three-dimensional turbulent shear layer in the vicinity of an appendage mounted perpendicular to a flat plate. The thickness of the turbulent boundary layer as it approached the appendage leading edge was 76 mm or 1.07 times the maximum thickness of the appendage. As the oncoming boundary layer passed around the appendage, a strong secondary flow was formed which was dominated by a horseshoe root vortex. This secondary flow had a major effect in redistributing both the mean flow and turbulence quantities throughout the shear layer, and this effect persisted to a significant degree up to at least three chord lengths downstream of the appendage leading edge.

Drainage and filling in cylindrical and rectangular containers

Abstract Drainage and filling processes in cylindrical and rectangular containers for several motion sequences are experimentally studied using a stereo videogrammetric technique. The measured quantities include the rigid body motion of the containers and the water level relative to the body coordinate system as a function of time. The experimental data are used to validate Torricellis law and determine the time constant, discharge coefficient, and water volume. In addition, the air funnel shapes in vortical sinks in a stationary cylinder are measured, and the effects of the initial water height and swirling on the drainage are addressed.

Underhood Buoyancy Driven Flow—An Experimental Study

Particle image velocimetry and thermal measurements using thermocouples are used to measure the buoyant flow of a simplified full-scale model of an engine compartment. The engine block surface temperature and exhaust heaters are kept at about 100 and 600°C, respectively. Thermal measurements include enclosure surface temperature, temperature difference on the enclosure wall at midplane, engine block temperatures, and air temperatures under the hood. The highest surface temperatures were concentrated near the top of the enclosure around the exhaust heaters. This effect was due primarily to radiation from the exhaust heaters. Highest measured air temperature was about 300°C immediately above the right exhaust heater. The measured dominant flow structures are two larger counter rotating vortices over the top right side of the engine block and two counter rotating vortices over the top left side. These flow structures weaken considerably during the first 35 min of the transient cool down of the engine block and the exhaust heaters. Colder ambient air is sucked into the engine compartment at the vents near the bottom of the compartment with some exiting as hot air through the top slots. The time scale of the fluid exchange at the vents is in the order of seconds, indicating that this process is occurring very slowly.

The interaction between a plane shear layer and a slender body

Abstract The interaction of a plane shear layer with a thin flat plate located in the nonlinear region of the shear layer has been investigated experimentally. The shear layers velocity ratio is 0.375, and its Reynolds number is ϱΔUθ 0 / μ = 625. It is found that for different angles of attack of the plate, the mixing layer is deflected toward the slower stream. In addition, the plate attenuates turbulent fluctuations of the shear layer structures.

A vortex flow intensified by thermal convection

This paper describes a thermal-convection-intensified vortex flow within a rotating cylinder with a counter-rotating heated disk located below. This flow tends to mimic certain aspects of the intriguing flow structure of the great red spot in Jupiter by using a simple laboratory setup. Particle image velocimetry measurements reveal the counter-rotating torus vortices in the lower and upper domains and the complex mixing-layer features in the transitional domain between them. In particular, it is found that the vortex structures are significantly intensified by the thermal convection from the heated disk.