我在使用Matplotlib的箭袋情节时遇到了一些问题.给定速度矢量场,我想在流线上绘制速度矢量.矢量与预期的流函数不相切.

为了计算流函数,我使用了Pankratov博士的Matlab代码的Python翻译版本,可在http://www-pord.ucsd.edu/~matlab/stream.htm获得(我的很快将在GitHub上提供).

使用其结果,我使用此代码：

import numpy

import pylab

# Regular grid coordineates, velocity field and stream function

x, y = numpy.meshgrid(numpy.arange(0, 21), numpy.arange(0, 11))

u = numpy.array([[10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,

27, 28, 29, 30],

[ 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,

26, 27, 28, 29],

[ 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,

25, 26, 27, 28],

[ 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,

24, 25, 26, 27],

[ 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,

23, 24, 25, 26],

[ 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,

22, 23, 24, 25],

[ 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,

21, 22, 23, 24],

[ 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,

20, 21, 22, 23],

[ 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,

19, 20, 21, 22],

[ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,

18, 19, 20, 21],

[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,

17, 18, 19, 20]])

v = numpy.array([[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,

13, 14, 15, 16, 17, 18, 19, 20],

[ -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,

12, 13, 14, 15, 16, 17, 18, 19],

[ -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,

11, 12, 13, 14, 15, 16, 17, 18],

[ -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,

10, 11, 12, 13, 14, 15, 16, 17],

[ -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,

9, 10, 11, 12, 13, 14, 15, 16],

[ -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7,

8, 9, 10, 11, 12, 13, 14, 15],

[ -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6,

7, 8, 9, 10, 11, 12, 13, 14],

[ -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5,

6, 7, 8, 9, 10, 11, 12, 13],

[ -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4,

5, 6, 7, 8, 9, 10, 11, 12],

[ -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3,

4, 5, 6, 7, 8, 9, 10, 11],

[-10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2,

3, 4, 5, 6, 7, 8, 9, 10]])

psi = numpy.array([[ 0. , 0.5, 2. , 4.5, 8. , 12.5, 18. , 24.5,

32. , 40.5, 50. , 60.5, 72. , 84.5, 98. , 112.5,

128. , 144.5, 162. , 180.5, 200. ],

[ -9.5, -10. , -9.5, -8. , -5.5, -2. , 2.5, 8. ,

14.5, 22. , 30.5, 40. , 50.5, 62. , 74.5, 88. ,

102.5, 118. , 134.5, 152. , 170.5],

[ -18. , -19.5, -20. , -19.5, -18. , -15.5, -12. , -7.5,

-2. , 4.5, 12. , 20.5, 30. , 40.5, 52. , 64.5,

78. , 92.5, 108. , 124.5, 142. ],

[ -25.5, -28. , -29.5, -30. , -29.5, -28. , -25.5, -22. ,

-17.5, -12. , -5.5, 2. , 10.5, 20. , 30.5, 42. ,

54.5, 68. , 82.5, 98. , 114.5],

[ -32. , -35.5, -38. , -39.5, -40. , -39.5, -38. , -35.5,

-32. , -27.5, -22. , -15.5, -8. , 0.5, 10. , 20.5,

32. , 44.5, 58. , 72.5, 88. ],

[ -37.5, -42. , -45.5, -48. , -49.5, -50. , -49.5, -48. ,

-45.5, -42. , -37.5, -32. , -25.5, -18. , -9.5, 0. ,

10.5, 22. , 34.5, 48. , 62.5],

[ -42. , -47.5, -52. , -55.5, -58. , -59.5, -60. , -59.5,

-58. , -55.5, -52. , -47.5, -42. , -35.5, -28. , -19.5,

-10. , 0.5, 12. , 24.5, 38. ],

[ -45.5, -52. , -57.5, -62. , -65.5, -68. , -69.5, -70. ,

-69.5, -68. , -65.5, -62. , -57.5, -52. , -45.5, -38. ,

-29.5, -20. , -9.5, 2. , 14.5],

[ -48. , -55.5, -62. , -67.5, -72. , -75.5, -78. , -79.5,

-80. , -79.5, -78. , -75.5, -72. , -67.5, -62. , -55.5,

-48. , -39.5, -30. , -19.5, -8. ],

[ -49.5, -58. , -65.5, -72. , -77.5, -82. , -85.5, -88. ,

-89.5, -90. , -89.5, -88. , -85.5, -82. , -77.5, -72. ,

-65.5, -58. , -49.5, -40. , -29.5],

[ -50. , -59.5, -68. , -75.5, -82. , -87.5, -92. , -95.5,

-98. , -99.5, -100. , -99.5, -98. , -95.5, -92. , -87.5,

-82. , -75.5, -68. , -59.5, -50. ]])

# The plots!

pylab.close('all')

pylab.ion()

pylab.figure(figsize=[8, 8])

pylab.contour(x, y, psi, 20, colors='k', linestyles='-', linewidth=1.0)

pylab.quiver(x, y, u, v, angles='uv', scale_units='xy', scale=10)

ax = pylab.axes()

ax.set_aspect(1.)

产生以下结果来说明我的问题.

显然计算很好,但速度矢量与流函数不相符,正如预期的那样.使用精确的保存值,Matlab会生成一个箭头图,可以准确显示我想要的内容.在我的例子中,将宽高比设置为1可以得到所需的结果,但强制轴矩形具有特定的宽高比.

ax = pylab.axes()

ax.set_aspect(1.)

我已经尝试过不同的参数,比如’单位’,’角度’或’比例’.

是否有人知道如何制作适应画布宽高比并且仍然与我的轮廓线相切的箭头图,如预期的那样？

我期望得到与此类似的结果(注意向量如何与流线相切)：

非常感谢！