Howard H. Hu

Blade tip timing (BTT) is a special non-contact blade health monitoring technology. Lots of methods to analyze and recover BTT signal have been developed. However, the effects of signal non-uniformity on signal recovery and parameter identification have not been fully addressed. In this paper, the influence of signal non-uniformity on the parameter identification using two classical methods is studied. Simulation and experimental validation are performed to verify the proposed analysis method.

In this paper we study some basic problems of fluid dynamics of two incompressible miscible liquids modeled as a simple mixture in which the density of the mixture is connected to the densities of the two constituents by a linear relation in the volume fraction. Since the density of such a mixture of incompressible liquids is changed by diffusion, the expansion Δ = div u does not vanish in general. The velocity in such a mixture can be decomposed into a solenoidal and an expansion part. The expansion velocity is induced by diffusion which is proportional to the gradient of the volume fraction in a simple mixture. We find that the expansion velocity is always important where the gradients of the volume fraction are sufficiently great, most especially at early times in the mixing layer arising from the smoothing of an initial plane or spherical discontinuity of composition. Another case and place where divu = 0 may be bad approximation is in driven problems of mixing layer where gradients of composition (or volume fraction) can be maintained in a competition between convection and diffusion.