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Due to the rapid development in many parts of Egypt, construction of a wide road network is maintaining a rapid pace. But, those roads are affected by the overcrowded big cities. Thus, there is a growing need for driving tunnels to reduce the traffic problems and facilitate transportation. This issue is highly related to economic (fuel consumption) and environmental (pollution and noise) matters. Up to our knowledge, this paper represents the first numerical study to concern driving tunnels in the Middle East. Actual domestic tunnels and vehicles are computationally simulated. Investigations concentrate on flow behavior, especially overall drag coefficient and wake structure behind vehicles. Results show that many parameters, such as tunnel height, and vehicle height and speed, affect the aerodynamic characteristics through driving tunnels.

This research work is concerned with experimental studies of the aerodynamic interference between passenger cars. Aerodynamic interference covers the two cases of vehicles in a convoy and in parallel passing (overtaking). Vehicles are assumed to be moving in open roads. Flow visualization technique is used to clarify the flow behavior, especially wake structure behind interfering passenger cars. This paper is a trial to further explain the aerodynamic characteristics, usually reported in the form of pressure distributions and drag forces, through visible observations. Visualization images of passenger cars in close interference are presented for the first time. Special attention is paid to the effect of Reynolds number on flow pattern especially in severe interference conditions. Results show that flow structure around interfering cars changes dramatically depending on the gap between the cars and Reynolds number. Interesting flow structures are captured and analyzed.