Methods for calculating the profile drag of airfoils in incompressible and compressible flows are presented respectively. Both methods are constructed by the current. boundany layer theories which have reasonable accuracy. In these method ghe calculated or experimental pressure distributions on airfoils must be given in advance.
Profile drag has been calculated by these methods for several airfoils in both incompressible flow and subcritical subsonic flow at various lift coefficients and Reynolds numbers. Comparison of the results with available experimental data show good agreement.

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On the basis of nonlinear theory, the axisymmetric dynamic deformations produced in viscoelastic clamped shallow spherical sheils by transient pressure loading are analyzed. Two types of loading condition, that is, a step loading and a graded loading, are considered and the three-element model is used to describe the viscoelastic characteristics of the material considered. The governing equations derived by the authors are solved numerically, and the critical loads and the effects of viscoelasticity and loading speed on the dynamic behavior of the shell are discussed. And it is pointed out that Che buckling phenomena have to be analyzed paying an attention to the connection with the time, because the dynamic, static and creep bucklings are related with one another as a function of time. From the xesults of the present numerical solutron, the quasi-static buckling load also is obtained immediately, which differs little from the static buckling load reported so far. The procedure adopted in the present analysis can be applied easily to the problems of elastic shells. The dynamic behavior of elastic shallow spherical shell obtained, by the present procedure is compared with the previous results and an excellent agreement between them is seen.

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