## THERMAL SCIENCE

International Scientific Journal

### AN APPLICATION OF CHAOS GRAY-ENCODED GENETIC ALGORITHM FOR PHILIP INFILTRATION MODEL

**ABSTRACT**

To improve the precision of parameters' estimation in Philip infiltration model, chaos gray-coded genetic algorithm was introduced. The optimization algorithm made it possible to change from the discrete form of time perturbation function to a more flexible continuous form. The software RETC and Hydrus-1D were applied to estimate the soil physical parameters and referenced cumulative infiltration for seven different soils in the USDA soil texture triangle. The comparisons among Philip infiltration model with different numerical calculation methods showed that using optimization technique can increase the Nash and Sutcliffe efficiency from 0.82 to 0.97, and decrease the percent bias from 14% to 2%. The results indicated that using the discrete relationship of time perturbation function in Philip infiltration model's numerical calculation underestimated model's parameters, but this problem can be corrected a lot by using optimization algorithm. We acknowledge that in this study the fitting of time perturbation function, Chebyshev polynomial with order 20, did not perform perfectly near saturated and residue water content. So exploring a more appropriate function for representing time perturbation function is valuable in the future.

**KEYWORDS**

PAPER SUBMITTED: 2017-12-05

PAPER REVISED: 2017-12-12

PAPER ACCEPTED: 2017-12-13

PUBLISHED ONLINE: 2018-09-09

**THERMAL SCIENCE** YEAR

**2018**, VOLUME

**22**, ISSUE

**4**, PAGES [1581 - 1588]

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