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发表于 2008-10-10 16:04:32
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来自 北京
问题解决了
问题解决了。确实是因为有效数字位数的问题。我在matlab中利用写文件,将BH数据导出。此时可以控制位数,因此我将BH数据的小数点后面的位数增加为6位。同样还是顶端最开始提到的H^2的构造方式,但是按照这个多位数输出的数据输入ansys,ansys就不提示那个final slope的问题了。
此时我们来计算一下按照这个数据进行计算最后一个点的final slope(按照自己的理解,就是前向差分)
最后两个点为:
TBPT,, 180747.312501, 2.107975
TBPT,, 216751.120201, 2.153222
那么final slope=(2.153222-2.107975)/(216751.120201-180747.312501)=1.25672818766888e-006
而Muo=4*pi*1E-7=1.25663706143592e-006
因此,可以看到,利用这个多位数的数据进行计算,的确是比空气的磁导率要高的。虽然不知道ansys是如何计算的,但是ansys现在不提示了,而且我们利用这些数据进行计算尾部的final slope也是比空气的磁导率高的。
而最初直接拷贝出的有效数字位数少的时候,利用最后两个点计算的final slope的确也是比空气的磁导率要小,虽然和ansys提示的final slope数值不同,但是ansys提示的应该是有道理的。
我想,这个问题到此应该可以结束了。
小结:
(1)自己构造BH曲线的时候,给出BH数据点的有效位数要合适。最起码要自己保证最后两个点计算的斜率不要比空气Muo小
(2)第一个点可以是0,0;也可以不是0,0吧。这个我通过计算发现是相同的。如果谁有更加确切的理解,请不吝赐教。
(3)ansys中给出的final slope的提示是有道理的。往往可以提醒我们再次检查BH曲线是否的确延伸斜率小于Muo
(4)ansys中给出的final slope不知道是按照什么计算方法进行的。
代码见下:
fid = fopen('BH.txt', 'wt');
fprintf(fid, 'TB,BH,2,,%d\n',length(H));
fprintf(fid, 'TBPT,,%20.6f, %20.6f\n', BH');
fclose(fid)
数据见下:
TB,BH,2,,103
TBPT,, 0.000000, 0.000000
TBPT,, 0.100000, 0.000172
TBPT,, 36.508700, 0.062904
TBPT,, 72.917400, 0.125637
TBPT,, 109.326100, 0.188369
TBPT,, 145.734800, 0.251101
TBPT,, 182.143500, 0.313833
TBPT,, 218.552200, 0.376565
TBPT,, 254.960900, 0.439298
TBPT,, 291.369600, 0.502030
TBPT,, 327.778300, 0.564762
TBPT,, 364.187000, 0.627494
TBPT,, 400.595700, 0.690226
TBPT,, 437.004400, 0.752959
TBPT,, 473.413100, 0.815691
TBPT,, 509.821800, 0.878423
TBPT,, 546.230500, 0.941155
TBPT,, 582.639200, 1.003887
TBPT,, 619.047900, 1.066620
TBPT,, 655.456600, 1.129352
TBPT,, 691.865300, 1.192084
TBPT,, 728.274000, 1.254816
TBPT,, 728.374000, 1.254988
TBPT,, 728.394000, 1.255023
TBPT,, 728.418000, 1.255064
TBPT,, 728.446800, 1.255114
TBPT,, 728.481360, 1.255173
TBPT,, 728.522832, 1.255245
TBPT,, 728.572598, 1.255330
TBPT,, 728.632318, 1.255433
TBPT,, 728.703982, 1.255556
TBPT,, 728.789978, 1.255704
TBPT,, 728.893174, 1.255882
TBPT,, 729.017008, 1.256094
TBPT,, 729.165610, 1.256350
TBPT,, 729.343932, 1.256656
TBPT,, 729.557918, 1.257022
TBPT,, 729.814702, 1.257462
TBPT,, 730.122843, 1.257990
TBPT,, 730.492611, 1.258621
TBPT,, 730.936333, 1.259378
TBPT,, 731.468800, 1.260285
TBPT,, 732.107760, 1.261370
TBPT,, 732.874512, 1.262668
TBPT,, 733.794614, 1.264221
TBPT,, 734.898737, 1.266077
TBPT,, 736.223685, 1.268293
TBPT,, 737.813622, 1.270936
TBPT,, 739.721546, 1.274085
TBPT,, 742.011055, 1.277832
TBPT,, 744.758466, 1.282283
TBPT,, 748.055359, 1.287560
TBPT,, 752.011631, 1.293801
TBPT,, 756.759158, 1.301162
TBPT,, 762.456189, 1.309813
TBPT,, 769.292627, 1.319943
TBPT,, 777.496352, 1.331748
TBPT,, 787.340823, 1.345430
TBPT,, 799.154187, 1.361187
TBPT,, 813.330225, 1.379196
TBPT,, 830.341470, 1.399604
TBPT,, 850.754964, 1.422496
TBPT,, 875.251157, 1.447884
TBPT,, 904.646588, 1.475671
TBPT,, 939.921106, 1.505641
TBPT,, 982.250527, 1.537436
TBPT,, 1033.045832, 1.570559
TBPT,, 1094.000199, 1.604390
TBPT,, 1167.145439, 1.638215
TBPT,, 1254.919726, 1.671278
TBPT,, 1360.248872, 1.702845
TBPT,, 1486.643846, 1.732264
TBPT,, 1638.317815, 1.759023
TBPT,, 1820.326578, 1.782787
TBPT,, 2038.737094, 1.803411
TBPT,, 2300.829712, 1.820929
TBPT,, 2615.340855, 1.835523
TBPT,, 2992.754226, 1.847486
TBPT,, 3445.650271, 1.857173
TBPT,, 3989.125525, 1.864968
TBPT,, 4641.295830, 1.871247
TBPT,, 5423.900196, 1.876364
TBPT,, 6363.025435, 1.880635
TBPT,, 7489.975722, 1.884336
TBPT,, 8842.316067, 1.887710
TBPT,, 10465.124480, 1.890966
TBPT,, 12412.494576, 1.894291
TBPT,, 14749.338692, 1.897857
TBPT,, 17553.551630, 1.901831
TBPT,, 20918.607156, 1.906379
TBPT,, 24956.673787, 1.911679
TBPT,, 29802.353744, 1.917928
TBPT,, 35617.169693, 1.925347
TBPT,, 42594.948832, 1.934195
TBPT,, 50968.283798, 1.944772
TBPT,, 61016.285758, 1.957437
TBPT,, 73073.888109, 1.972616
TBPT,, 87543.010931, 1.990818
TBPT,, 104905.958318, 2.012650
TBPT,, 125741.495181, 2.038842
TBPT,, 150744.139417, 2.070267
TBPT,, 180747.312501, 2.107975
TBPT,, 216751.120201, 2.153222 |
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