In recent years, experimental results obtained by means of the wake survey method have indicated that the viscous drag of a ship model varies with the Froude number; later studies have tended to confirm these findings. The present work was undertaken to establish the validity of this variation. In order to avoid the principal sources of inaccuracy of previous work, modifications to the equipment were made. Also, to obtain viscous drag, the authors applied a refinement of the Betz-Tulin formula.

Predicted and measured surface velocity and pressure distributions in the internal flow channels of a centrifugal fan impeller are presented for volume flow rates between 80 and 125 percent of design flow rate. Predictions are based on a fully three-dimensional, finite element analysis of the inviscid, incompressible blade channel flow. Additional predictions using a conventional quasi-three-dimensional analysis are presented for comparison. Experimental results were developed using extensive blade and sidewall surface pressure taps installed in a scale model of an airfoil-bladed centrifugal fan impeller designed for heavy industrial and power generation applications. The results illustrate the ability of both flow analyses to predict the dominant features of the impeller flow field, including peak blade surface velocities and adverse gradients at flows far from the design point. In addition, the experimental results provide valuable insight into the limiting channel diffusion values for typical centrifugal cascade performance, and the influence of viscous effects as seen in deviations from the ideal flow predictions.

Analytical and experimental procedures for determining the detailed internal flow behavior in the impeller of a centrifugal fan are presented. Predicted and measured values of both the detailed flow fields and overall performance of the impeller are shown to be in good agreement. The analytical procedures are based on a finite element method to predict the inviscid flow field, coupled to a semi-empirical determination of pressure losses in the impeller based on boundary layer calculations. The experimental work used to validate these predictions uses extensive surface pressure taps in the rotating impeller as well as information from inlet and discharge velocity traverses to determine overall performance. The purpose of this work is the development of accurate and reliable analytical tools for the design of air and gas moving equipment with improved performance and efficiency for the power utility market and heavy industrial applications.

One of the assumptions of Eggers' method for measuring wavemaking resistance, that the effects of the near-field surface disturbance may be neglected, is investigated analytically for a family of vertical struts extending to various depths. It is found that the error in Eggers' transverse-cut method is less than 1 percent at strut drafts of shiplike dimensions, if surface profiles at downstream distances greater than one model length are used. For vertical struts, errors of about 5 percent would be expected for struts of drafts of about half to three times the model length at downstream distances between one and two model lengths. A graphical procedure for minimizing the errors due to the aforementioned assumption is proposed.

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