Performance of Mixed Lubrication—Numerical and Experimental Studies

5 Performance of Mixed Lubrication— Numerical and Experimental Studies 

Autocorrelation function provides the information as for how the random heights are correlated to each other. The ACF in two-dimensional form is defined as 

Consequently, the surface generation becomes a question of producing a matrix of random data that obey the defined height distribution and a prescribed ACF This can be carried out efficiently through the procedure of a 2-D digital filter, proposed by Hu and Tonder [47], as summarized as follows. 

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Suppose rj i,/) is a sequence of random numbers produced by computer generation, which takes a Gaussian distribution of a known standard deviation cr, the target roughness heights z i,/) that obeys a given ACF can be written as 

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