Differential- Simplex Algorithm Applied Research In Estimating Anisotropic Aquifer Parameters

Aquifer parameters are basic parameters to evaluate groundwater resources,also are the fundamental basis for the establishment of groundwater flow model. Its reliability will directly influence the authenticity and the reliability of groundwater simulation and calculation results. And it has very important significant guiding for the rational planning of water wells, the reasonable exploiting of groundwater, maintaining ecological balance. At present, the most important way to determine the aquifer parameters is based on the analytical solution, through the analysis of pumping experiment data, then using intelligent optimization algorithm to determine the aquifer parameters.In view of the advantages and disadvantages in each intelligent optimization algorithm,We have combined differential evolution algorithm which has a strong global search ability with simplex algorithm which has a strong local search ability, to form an differential-simplex algorithm. We respectively applied differential evolution algorithm, simplex algorithm and differential- simplex algorithm to analyze anisotropic aquifer under the condition of experiment data then determine the anisotropy aquifer parameters. Basing on the results of the numerical experiment to discuss the advantage of differential- simplex algorithm in determining the aquifer parameters. The important research work is as follows:(1) First of all we have discussed advantages and disadvantages of differential evolution algorithm and the simplex algorithm, And then combining their respective advantages and overcoming the shortcomings of each other, Constructing differential- simplex algorithm which can effectively balance the global search and the local search;(2) Using differential- simplex algorithm to solve anisotropic aquifer parameters, By comparing calculation results with other methods in some references, Fitting With the actual calculation results, You can see differential- simplex algorithm can accurately and effectively used to determine the anisotropic aquifer parameters; Using the differential- simplex algorithm and separately differential evolution algorithm and the simplex algorithm to solve the anisotropic aquifer parameters, By comparing the calculation results, calculation accuracy and optimization rate, we know that the algorithm overcomes the shortcoming of differential evolution algorithm and simplex algorithm for solving anisotropic aquifer parameters;(3) In this paper, we discussed the relation between interleaving, sequence length,contraction coefficient, number of iterations, the algorithm running time in differential-simplex algorithm in solving the anisotropy aquifer parameters, It is concluded that thealgorithm in solving the problem, the suitable value of interleaving is 0.6 or 0.8, the sequence length is suitable for 200-400,and the contraction coefficient is suitable for 0.5. At this point not only ensure the calculation precision of the algorithm but also avoid wasting time, and effectively improve the performance of the algorithm.(4) The water level in the calculation example is disturbed by different degrees disturbance, Then conducting numerical experiments, The experimental results showed that,The method as compared with other methods has good stability; With the increase of disturbance degree, The calculation results appear tiny changes; This requires that in the process of field experiment to ensure the authenticity and reliability of the measured data, as far as possible to minimize data errors.