应用背景使用了简单的显示格式，对计算步长有严格限制，但程序编写简单。欢迎就算法，编程等问题交流
参考文献：Problem 1 (p.446), chapter 9, Computational Fluid Dynamics, The Basics with Applications, John D. Anderson, JR. McGraw-Hill, 2002, 4关键技术编写的一个简单程序，用于计算水力学学习。非守恒型控制方程，显式中心差算法。
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001105s ]
SELECT `a`.`aid`,`a`.`title`,`a`.`create_time`,`m`.`username` FROM `jrk_downrecords` `a` INNER JOIN `jrk_member` `m` ON `a`.`uid`=`m`.`id` WHERE `a`.`status` = 1 GROUP BY `a`.`aid` ORDER BY `a`.`create_time` DESC LIMIT 10 [ RunTime:0.071075s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001030s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.001082s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.000902s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.003212s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.000811s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.003758s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.015894s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001202s ]
UPDATE `jrk_articles` SET `hits` = 2 WHERE `id` = 213478 [ RunTime:0.015297s ]
