Reviewing a classical Persian book on ground‐water problems of the 11th century, it is shown that Ground‐water hydrology developed absolutely independently of geology. The Arabic‐Persian scientists of that time knew about the hydrologic cycle and the existence of different types of water underground; and they knew that the quality of water depends on the character of the rocks through which ground water flows. Techniques of developing ground‐water resources in the Middle East, i.e., the digging of wells and qanats, were of such a high standard that they are still in use today. Generally, it can be stated that the oriental scientists of the Middle Ages knew of the basic principles of hydrology. Thus they were far ahead of their contemporaries in Europe.

Matching diagram is a key part of the conceptual design process to determine the wing area and the required power. However, it requires drag polar estimation and the assumption of maximum lift coefficient. In case of conventional manned aircraft, early estimation techniques are based on statistical data that are not suitable for hand-launched aircraft. In this study, it has been attempted to present the performance calculations and a proper conceptual design model by acquiring sound values for the aerodynamic coefficients in low Reynolds number, using statistical wetted area as well as a raw design of fuselage, wing and tails. The process is applied to a sample scenario and the results are evaluated.

No abstract

No abstract

No abstract