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 Visualization and Analysis of  V/STOL Twin Jet Flow

Yasser M El-Okda

Engineering Science and Mechanics Department

The Vertical Short Take-off and Landing (VSTOL) aircraft is one of the promising aircraft configurations. They are expected to play an important part in Military missions as well as in transportation industry in the future. As the name implies, this Aircraft is designed to take-off, hover, and land vertically like a helicopter. However, it has the advantage over the helicopter that it can fly with the speed, range, and efficiency of a fixed-wing airplane. There are a few  configurations of the lift power source. Some of the V/STOL models have twin jet engine in a tandem arrangement with respect to the flow. The Jets are mounted so that they can rotate 90 degrees between vertical and horizontal positions. The thrust of the vertical jets provides for vertical take-off and vertical landing. Rotating the jets to assume the horizontal position, they provide the V/STOL aircraft with a sufficient accelerating thrust in order to achieve high speed cruse. Other models adapt the same twin for only the vertical STOL operation. An example of that is the Boeing version of the Joint Strike Fighter (JSF) aircraft. On the other side The Lockheed Martin JSF version exploits two successive vertical trust jets to achieve the vertical STOL operation in which the rear jet is rotated to assume the horizontal position to accelerate the aircraft.

The flow of the jets , with tandem arrangement with respect to the flow, when positioned vertically is investigated. A model of a plate with two jets impinging against the floor of the water tunnel in the ESM Dept. Fluid Mechanics Laboratory. The flow of the jets and the their interaction with the ground (the tunnel floor) is investigated. The jet flow was investigated with and without free stream velocity.

This investigation aims to prove that there is natural unsteadiness of the up wash flow arising from the impingement of the tandem jet arrangement on the ground.

Particle Image Velocimetry Technique is one of the greatest facilities in the ESM fluid Mechanics Laboratory. The technique is useful in both flow visualization and velocity measurement. The date is to be collected as flow images for both the visualization and the analysis. Then, Processing the images will be done by the a retail software package to extract the velocity field. Post processing will be done by C++ code for calculation of different flow field properties. With TechPlot retail software, animations and images extraction together with different plots will be done.


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