Fathi Finaish

Further Visualization of Combined Wing Tip and Starting Vortex Systems

Visualisation des systemes de tourbillons dans un ecoulement demarrant a acceleration constante

Starting Flow Over Spoilers, Double Steps and Cavities

The development of two-dimensional vortex patterns in accelerating flow starting from rest has been investigated by streakline visualization and documented in photographic sequences. We considered flow over spoilers, double steps and cavities. A limited parametric analysis is provided for some of the photographic results.

On vortex structures and processes over bluff bodies in impulsive flow

An experimental system that generates and visualizes unsteady motions in air was employed to visualize vortex developments over bluff bodies in impulsive started flow. The study presents photographic sequences of impulsive flow over circular and square cylinders for flow Reynolds number of 200. A comparison of physical and numerical visualization for impulsive flow over a flat plate at 50° angle of attack and for flow Reynolds number of 1,000 is also presented. The visualization examples reveal the details of vortex separation and subsequent developments and may be utilized as a reference to guide and economize computer visualization efforts on unsteady separated flows.

Visualization of the vortex street behind a circular cylinder at low Reynolds numbers

Vortical filament development behind a circular cylinder immersed in steady flow is documented in photographic sequences at Reynolds numbers 70, 120, and 300.

Parametric Study of Motor/Shroud Heat Transfer Performance in an Electrical Submersible Pump (ESP)

A shroud is commonly used around the motor of an electrical submersible pump (ESP) to accelerate reservoir fluids past the motor for cooling. Standard practice has been to design the shroud/motor configuration relative to the casing using a minimum fluid velocity of 0.3048 m/s (I ft/s) rule of thumb as a production strategy. The increase in the use of ESPs to exploit heavy oil reservoirs has brought up the necessity of revising this rule in order to prevent motor burnouts. A parametric study has been conducted using the computational fluid dynamics software CFX4.2 to examine the heat transfer behavior of the shroud motor configuration as a function of motor/shroud standoff. The objective of this effort is to examine the validity of the historical rule of thumb for heavy oils. Results for a case study on an oil with a viscosity of 78 cp @ 320 K are presented. Further, to explore the possibility of enhancing the heat transfer characteristics, the flow configuration was modified by incorporating several openings on the shroud. Based on the obtained results, it can be concluded that fluid velocity should be kept around 0.85 m/s (2.8 ft/s) as opposed to 1 ft/s to assure proper cooling of the motor. Also, flow redistribution by proper placement of the slots on the shroud may produce better heat transfer between the oil and the motor wall.

A parametric analysis of vortex patterns visualized over airfoils in accelerating flow

Complex vertical patterns form over the surface of an airfoil in an accelerating flow started from rest. A parametric analysis of the development of the vortex patterns was conducted, using flow visualization data. We focused on the dependence of the vortex development on angle of attack and on Reynolds number. This analysis helps understanding of complex unsteady flows and it may serve as a reference for numerical models and for computer simulation

Flow Resistance Characteristics of Airflow Control Dampers (RP-1157)

This paper presents the experimental results of the performance of various types of HVAC system airflow control dampers over a wide range of types, installations, and operating conditions. Three hundred and sixty-eight tests have been conducted with the data and results discussed herein. The main fundamental performance parameter for predicting the flow rate through a partially opened damper is the pressure loss coefficient as a function of the degree of damper opening. Major variables included the type of damper, blade movement, manufacturer, installation, approach velocity, and total system pressure drop. Results should prove very useful for HVAC system designers in the proper selection of airflow modulating dampers.

Gaseous Mixing Characteristics of Parallel Blade Damper Combinations (RP-1045)

Concern for indoor air quality continues to have a significant impact on the design and operation of heating, ventilating, and air-conditioning (HVAC) systems. A major player in the performance of such systems is the flow control damper, particularly with the current popularity of the variable air volume type of system. Mixed air damper systems with economizer control have been used for many years to provide energy savings and to provide ventilation air for building occupants. It is often assumed that sufficient mixing of the outdoor air and return air occurs if parallel blade dampers properly aligned are used. However, it has been found that some mixed air dampers do not provide proper mixing of air under cold outdoor air temperature conditions. If the thermal mixing is inadequate to prevent coil freezing, there may also be inadequate mixing of oxygen and gaseous contaminants that could lead to poor indoor air quality (IAQ). This paper includes guidelines for the selection of mixed air damper configurations that provide proper mixing of airstreams. Configurations that do not provide proper mixing are also identified.