Dynamic Anticumulative Protection. II

Various types of dynamic anticumulative protection and the effect of its parameters on jet penetration into a target were studied.     

Improving mass conservation in simulation of incompressible flows

We propose a technique for improving mass‐conservation features of fractional step schemes applied to incompressible flows. The method is illustrated by using a Lagrangian fluid formulation, where the mass loss effects are particularly apparent. However, the methodology is general and could be used for fixed grid approaches. The idea consists in reflecting the incompressibility condition already in the intermediate velocity. This is achieved by predicting the end‐of‐step pressure and using this prediction in the fractional momentum equation. The resulting intermediate velocity field is thus much closer to the final incompressible one than that of the standard fractional step scheme. In turn, the predicted pressure can be used as the boundary condition necessary for the solution of the pressure Poisson equation in case a continuous Laplacian matrix is employed. Using this approximation of the end‐of‐step incompressible pressure as the essential boundary condition considerably improves the conservation of mass, specially for the free surface flows of fluids with low viscosity. The pressure prediction does not require the resolution of any additional equations system. The efficiency of the method is shown in two examples. The first one shows the performance of the method with respect to mass conservation. The second one tests the method in a challenging fluid–structure interaction benchmark, which can be naturally resolved by using the presented approach. Copyright © 2012 John Wiley & Sons, Ltd.     

Estimation of the Influence of a Lack of Simultaneity of Input Actions when Implementing a Method Utilizing Paired Transient Processes

The results of analytical investigations are given and expressions are obtained making it possible to estimate and eliminate errors of the amplitude-frequency and phase-frequency characteristics of an investigated system caused by a delay in the input action to all systems used in an experiment.     

Algorithms for Measuring the Quality of Products and Their Characteristics

The principles of synthesizing algorithms for measuring the quality of products are presented on the basis of the mean arithmetic, geometric, harmonic, and other components. The fundamental provisions for measuring the initial information utilizing virtual standards are discovered. A method based on a numerical experiment is proposed for verifying the effectiveness, validity, and bias of algorithms for measuring the quality of products and expressions are given for a generalized algorithm for measuring the quality of products which makes it possible to obtain the most effective and unbiased results.     

Verification of the effectiveness of an indirect method for estimating the dynamic characteristics of systems

A numerical experiment is proposed the essence of which is to compare accurate amplitude-frequency and phase-frequency characteristics with calculated characteristics determined using an indirect estimating method. The results of the calculations are presented in the form of graphs. It follows from the calculated data that the proposed method is highly accurate and is simple to implement. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 11–16, September, 1999.