File: osmap.f

package info (click to toggle)
xfoil 6.99.dfsg%2B1-1
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 8,776 kB
  • sloc: fortran: 43,375; ansic: 11,234; makefile: 379; pascal: 235; csh: 24
file content (492 lines) | stat: -rwxr-xr-x 15,558 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
      SUBROUTINE OSMAP(RSP,WSP,HSP,
     &                ALFR,
     &                ALFR_R, ALFR_W, ALFR_H,
     &                ALFRW_R,ALFRW_W,ALFRW_H ,
     &                ALFI,
     &                ALFI_R, ALFI_W, ALFI_H,
     &                ALFIW_R,ALFIW_W,ALFIW_H , OK)
C---------------------------------------------------------------------
C    
C     Returns real and imaginary parts of complex wavenumber (Alpha) 
C     eigenvalue from Orr-Sommerfeld spatial-stability solution 
C     with mean profiles characterized by shape parameter H.  
C     Also returns the sensitivities of Alpha with respect to the 
C     input parameters.
C
C     The eigenvalue Alpha(Rtheta,W,H) is stored as a 3-D array at 
C     discrete points, which is then interpolated to any (Rtheta,W,H)
C     via a tricubic spline.  The spline coordinates actually used are:
C
C       RL = log10(Rtheta)    
C       WL = log10(W) + 0.5 log10(Rtheta)
C       HL = H
C
C
C      Input:
C      ------
C        RSP      momentum thickness Reynolds number  Rtheta = Theta Ue / v
C        WSP      normalized disturbance frequency         W = w Theta/Ue
C        HSP      shape parameter of mean profile          H = Dstar/Theta
C
C      Output:
C      -------
C        ALFR     real part of complex wavenumber * Theta
C        ALFR_R   d(ALFR)/dRtheta
C        ALFR_W   d(ALFR)/dW
C        ALFR_H   d(ALFR)/dH
C        ALFRW_R  d(dALFR/dW)/dRtheta
C        ALFRW_W  d(dALFR/dW)/dW
C        ALFRW_H  d(dALFR/dW)/dH
C
C        ALFI     imag part of complex wavenumber * Theta
C        ALFI_R   d(ALFI)/dRtheta
C        ALFI_W   d(ALFI)/dW
C        ALFI_H   d(ALFI)/dH
C        ALFIW_R  d(dALFI/dW)/dRtheta
C        ALFIW_W  d(dALFI/dW)/dW
C        ALFIW_H  d(dALFI/dW)/dH
C
C        OK     T  if look up was successful; all values returned are valid
C               F  if point fell outside (RL,WL) spline domain limits; 
C                  all values (ALFR, ALFR_R, etc.) are returned as zero.
C                  Exception: If points only falls outside HL spline limits,
C                  then the HL limit is used and an ALFR value is calculated,
C                  but OK is still returned as F.
C                  
C---------------------------------------------------------------------
      LOGICAL OK
C
C
      REAL B(2,2), BR(2,2), BW(2,2), BH(2,2),
     &            BRW(2,2),BRH(2,2),BWH(2,2),BRWH(2,2)
      REAL C(2)  , CR(2)  , CW(2)  , CH(2)  ,
     &            CRW(2)  ,CRH(2)  ,CWH(2)  ,CRWH(2)
C
      REAL AINT(2),
     &     AINT_R(2), AINT_W(2), AINT_H(2),
     &     AINTW_R(2),AINTW_W(2),AINTW_H(2)
C
      PARAMETER (NRX=31, NWX=41, NHX=21)
      COMMON /AICOM_I/ NR, NW, NH,
     &               IC1, IC2,
     &               IW1(NHX), IW2(NHX), IR1(NHX),IR2(NHX)
C
C---------------------------------------------------------------
C---- single-precision OS data file
      REAL*4 RLSP, WLSP, HLSP,
     &    RINCR, WINCR, RL, WL, HL,
     &    A, AR, AW, AH, ARW, ARH, AWH, ARWH
C
C---- native-precision OS data file
c      REAL RLSP, WLSP, HLSP,
c     &    RINCR, WINCR, RL, WL, HL,
c     &    A, AR, AW, AH, ARW, ARH, AWH, ARWH
C---------------------------------------------------------------
C
      COMMON /AICOM_R/ RINCR, WINCR, RL(NRX), WL(NWX), HL(NHX),
     &                A(NRX,NWX,NHX,2),
     &               AR(NRX,NWX,NHX,2),
     &               AW(NRX,NWX,NHX,2),
     &               AH(NRX,NWX,NHX,2),
     &              ARW(NRX,NWX,NHX,2),
     &              ARH(NRX,NWX,NHX,2),
     &              AWH(NRX,NWX,NHX,2),
     &             ARWH(NRX,NWX,NHX,2)
C
      LOGICAL LOADED, NOFILE
      SAVE LOADED, NOFILE
C
C---- set OSFILE to match the absolute OS database filename
      CHARACTER*128 OSFILE
      INTEGER LOSF

      DATA OSFILE / '/var/local/codes/orrs/osmap.dat' /
c      DATA OSFILE
c     &/'/afs/athena.mit.edu/course/16/16_d0006/Codes/orrs/osmap_lx.dat'/
C
      DATA LOADED, NOFILE / .FALSE. , .FALSE. /
C
C---- set ln(10) for derivatives of log10 function
      DATA AL10 /2.302585093/
C
C
C---- set default returned variables in case of error, or OS map not available
      ALFR = 0.0
      ALFR_R = 0.0
      ALFR_W = 0.0
      ALFR_H = 0.0
      ALFRW_R = 0.0
      ALFRW_W = 0.0
      ALFRW_H = 0.0
C
      ALFI = 0.0
      ALFI_R = 0.0
      ALFI_W = 0.0
      ALFI_H = 0.0
      ALFIW_R = 0.0
      ALFIW_W = 0.0
      ALFIW_H = 0.0
C
      OK = .FALSE.
C
      IF(NOFILE) RETURN
C
      IF(LOADED) GO TO 9
C--------------------------------------------------------------------
C---- first time OSMAP is called ... load in 3-D spline data
C
      CALL GETOSFILE(OSFILE,LOSF)
      IF(LOSF.EQ.0) GO TO 800
C
      NR = 0
      NW = 0
      NH = 0
C
      LU = 31
      OPEN(UNIT=LU,FILE=OSFILE(1:LOSF),STATUS='OLD',
     &            FORM='UNFORMATTED',ERR=900)
C
      READ(LU) NR, NW, NH
C
      IF(NR.GT.NRX .OR.
     &   NW.GT.NWX .OR. 
     &   NH.GT.NHX     ) THEN
       WRITE(*,*) 'OSMAP: Array limit exceeded.'
       IF(NR.GT.NRX) WRITE(*,*) '       Increase NRX to', NR
       IF(NW.GT.NWX) WRITE(*,*) '       Increase NWX to', NW
       IF(NH.GT.NHX) WRITE(*,*) '       Increase NHX to', NH
       STOP
      ENDIF
C
      READ(LU) (RL(IR), IR=1,NR)
      READ(LU) (WL(IW), IW=1,NW)
      READ(LU) (HL(IH), IH=1,NH)
      READ(LU) (IR1(IH),IR2(IH),IW1(IH),IW2(IH), IH=1,NH)
C
      DO IC = 2, 1, -1
        DO IH=1, NH
          DO IW=IW1(IH), IW2(IH)
            READ(LU,END=5)
     &               (   A(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) (  AR(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) (  AW(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) (  AH(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) ( ARW(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) ( ARH(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) ( AWH(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
            READ(LU) (ARWH(IR,IW,IH,IC), IR=IR1(IH),IR2(IH))
          ENDDO
        ENDDO
      ENDDO
C
    5 CONTINUE
      IF(IH.LT.NH) THEN
C----- only imaginary part is available
       IC1 = 2
       IC2 = 2
      ELSE
C----- both real and imaginary parts available
       IC1 = 1
       IC2 = 2
      ENDIF
      CLOSE(LU)
C
C
      RINCR = (RL(NR) - RL(1))/FLOAT(NR-1)
      WINCR = (WL(NW) - WL(1))/FLOAT(NW-1)
      LOADED = .TRUE.
C
C--------------------------------------------------------------------
    9 CONTINUE
C
C
      IF(NR.EQ.0 .OR. NW.EQ.0 .OR. NH.EQ.0) THEN
C----- map not available for some reason (OPEN or READ error on osmap.dat?)
       OK = .FALSE.
       RETURN
      ENDIF
C
C---- define specified spline coordinates
      RLSP = ALOG10(RSP)
      WLSP = ALOG10(WSP) + 0.5*RLSP
      HLSP = HSP
C
C---- assume map limits will not be exceeded
      OK = .TRUE.
C
C---- find H interval
      DO IH = 2, NH
        IF(HL(IH) .GE. HLSP) GO TO 11
      ENDDO
      IH = NH
   11 CONTINUE
C
      IF(HLSP.LT.HL(1) .OR. HLSP.GT.HL(NH)) THEN
CCC       OK = .FALSE.
CCC       WRITE(*,*) 'Over H limits.  R w H:', RSP,WSP,HSP
CCC       RETURN
       HLSP = MAX( HL(1) , MIN( HL(NH) , HLSP ) )
      ENDIF
C
C---- find R interval
      IR = INT((RLSP-RL(1))/RINCR + 2.001)
      IR1X = MAX( IR1(IH) , IR1(IH-1) )
      IR2X = MIN( IR2(IH) , IR2(IH-1) )
      IF(IR-1.LT.IR1X .OR. IR.GT.IR2X) THEN
       OK = .FALSE.
CCC       WRITE(*,*) 'Over R limits.  R w H:', RSP,WSP,HSP
CCC       RETURN
       IR = MAX( IR1X+1 , MIN( IR2X , IR ) )
       RLSP = MAX( RL(1) , MIN( RL(NR) , RLSP ) )
      ENDIF
C
C---- find W interval
      IW = INT((WLSP-WL(1))/WINCR + 2.001)
      IW1X = MAX( IW1(IH) , IW1(IH-1) )
      IW2X = MIN( IW2(IH) , IW2(IH-1) )
      IF(IW-1.LT.IW1X .OR. IW.GT.IW2X) THEN
       OK = .FALSE.
CCC       WRITE(*,*) 'Over w limits.  R w H:', RSP,WSP,HSP
CCC       RETURN
       IW = MAX( IW1X+1 , MIN( IW2X , IW ) )
       WLSP = MAX( WL(1) , MIN( WL(NW) , WLSP ) )
      ENDIF
C
      DRL = RL(IR) - RL(IR-1)
      DWL = WL(IW) - WL(IW-1)
      DHL = HL(IH) - HL(IH-1)
      TR = (RLSP - RL(IR-1)) / DRL
      TW = (WLSP - WL(IW-1)) / DWL
      TH = (HLSP - HL(IH-1)) / DHL
C
      TR = MAX( 0.0 , MIN( 1.0 , TR ) )
      TW = MAX( 0.0 , MIN( 1.0 , TW ) )
      TH = MAX( 0.0 , MIN( 1.0 , TH ) )
C
C---- compute real and imaginary parts
      DO 1000 IC = IC1, IC2
C
C---- evaluate spline in Rtheta at the corners of HL,WL cell
      DO 20 KH=1, 2
        JH = IH + KH-2
        DO 205 KW=1, 2
          JW = IW + KW-2
          A1    = A   (IR-1,JW,JH,IC)
          AR1   = AR  (IR-1,JW,JH,IC)
          AW1   = AW  (IR-1,JW,JH,IC)
          AH1   = AH  (IR-1,JW,JH,IC)
          ARW1  = ARW (IR-1,JW,JH,IC)
          ARH1  = ARH (IR-1,JW,JH,IC)
          AWH1  = AWH (IR-1,JW,JH,IC)
          ARWH1 = ARWH(IR-1,JW,JH,IC)
C
          A2    = A   (IR  ,JW,JH,IC)
          AR2   = AR  (IR  ,JW,JH,IC)
          AW2   = AW  (IR  ,JW,JH,IC)
          AH2   = AH  (IR  ,JW,JH,IC)
          ARW2  = ARW (IR  ,JW,JH,IC)
          ARH2  = ARH (IR  ,JW,JH,IC)
          AWH2  = AWH (IR  ,JW,JH,IC)
          ARWH2 = ARWH(IR  ,JW,JH,IC)
C
          DA1   = DRL*AR1   - A2   + A1
          DA2   = DRL*AR2   - A2   + A1
          DAW1  = DRL*ARW1  - AW2  + AW1
          DAW2  = DRL*ARW2  - AW2  + AW1
          DAH1  = DRL*ARH1  - AH2  + AH1
          DAH2  = DRL*ARH2  - AH2  + AH1
          DAWH1 = DRL*ARWH1 - AWH2 + AWH1
          DAWH2 = DRL*ARWH2 - AWH2 + AWH1
C
C-------- set  ALFI, dALFI/dWL, dALFI/dHL, d2ALFI/dHLdWL
          B(KW,KH)   =  (1.0-TR)* A1   + TR* A2
     &               + ((1.0-TR)*DA1   - TR*DA2  )*(TR-TR*TR)
          BW(KW,KH)  =  (1.0-TR)* AW1  + TR* AW2
     &               + ((1.0-TR)*DAW1  - TR*DAW2 )*(TR-TR*TR)
          BH(KW,KH)  =  (1.0-TR)* AH1  + TR* AH2
     &               + ((1.0-TR)*DAH1  - TR*DAH2 )*(TR-TR*TR)
          BWH(KW,KH) =  (1.0-TR)* AWH1 + TR* AWH2
     &               + ((1.0-TR)*DAWH1 - TR*DAWH2)*(TR-TR*TR)
C
C-------- also, the RL derivatives of the quantities above
          BR(KW,KH)   = (A2   - A1
     &     + (1.0-4.0*TR+3.0*TR*TR)*DA1   + (3.0*TR-2.0)*TR*DA2  )/DRL
          BRW(KW,KH)  = (AW2  - AW1
     &     + (1.0-4.0*TR+3.0*TR*TR)*DAW1  + (3.0*TR-2.0)*TR*DAW2 )/DRL
          BRH(KW,KH)  = (AH2  - AH1
     &     + (1.0-4.0*TR+3.0*TR*TR)*DAH1  + (3.0*TR-2.0)*TR*DAH2 )/DRL
          BRWH(KW,KH) = (AWH2 - AWH1
     &     + (1.0-4.0*TR+3.0*TR*TR)*DAWH1 + (3.0*TR-2.0)*TR*DAWH2)/DRL
C
  205   CONTINUE
   20 CONTINUE
C
C---- evaluate spline in  HL  at the two WL-interval endpoints
      DO 30 KW=1, 2
        B1    = B   (KW,1)
        BR1   = BR  (KW,1)
        BW1   = BW  (KW,1)
        BH1   = BH  (KW,1)
        BRW1  = BRW (KW,1)
        BRH1  = BRH (KW,1)
        BWH1  = BWH (KW,1)
        BRWH1 = BRWH(KW,1)
C
        B2    = B   (KW,2)
        BR2   = BR  (KW,2)
        BW2   = BW  (KW,2)
        BH2   = BH  (KW,2)
        BRW2  = BRW (KW,2)
        BRH2  = BRH (KW,2)
        BWH2  = BWH (KW,2)
        BRWH2 = BRWH(KW,2)
C
        DB1   = DHL*BH1   - B2   + B1
        DB2   = DHL*BH2   - B2   + B1
        DBR1  = DHL*BRH1  - BR2  + BR1
        DBR2  = DHL*BRH2  - BR2  + BR1
        DBW1  = DHL*BWH1  - BW2  + BW1
        DBW2  = DHL*BWH2  - BW2  + BW1
        DBRW1 = DHL*BRWH1 - BRW2 + BRW1
        DBRW2 = DHL*BRWH2 - BRW2 + BRW1
C
C------ set  ALFI, dALFI/dRL, dALFI/dWL
        C(KW)   =  (1.0-TH)* B1   + TH* B2
     &          + ((1.0-TH)*DB1   - TH*DB2  )*(TH-TH*TH)
        CR(KW)  =  (1.0-TH)* BR1  + TH* BR2
     &          + ((1.0-TH)*DBR1  - TH*DBR2 )*(TH-TH*TH)
        CW(KW)  =  (1.0-TH)* BW1  + TH* BW2
     &          + ((1.0-TH)*DBW1  - TH*DBW2 )*(TH-TH*TH)
        CRW(KW) =  (1.0-TH)* BRW1 + TH* BRW2
     &          + ((1.0-TH)*DBRW1 - TH*DBRW2)*(TH-TH*TH)
C
C------ also, the HL derivatives of the quantities above
        CH(KW)   = (B2   - B1
     &     + (1.0-4.0*TH+3.0*TH*TH)*DB1   + (3.0*TH-2.0)*TH*DB2  )/DHL
        CRH(KW)  = (BR2  - BR1
     &     + (1.0-4.0*TH+3.0*TH*TH)*DBR1  + (3.0*TH-2.0)*TH*DBR2 )/DHL
        CWH(KW)  = (BW2  - BW1
     &     + (1.0-4.0*TH+3.0*TH*TH)*DBW1  + (3.0*TH-2.0)*TH*DBW2 )/DHL
        CRWH(KW) = (BRW2 - BRW1
     &     + (1.0-4.0*TH+3.0*TH*TH)*DBRW1 + (3.0*TH-2.0)*TH*DBRW2)/DHL
C
   30 CONTINUE
C
C---- evaluate cubic in  WL
      C1    = C   (1)
      CR1   = CR  (1)
      CW1   = CW  (1)
      CH1   = CH  (1)
      CRW1  = CRW (1)
      CRH1  = CRH (1)
      CWH1  = CWH (1)
      CRWH1 = CRWH(1)
C
      C2    = C   (2)
      CR2   = CR  (2)
      CW2   = CW  (2)
      CH2   = CH  (2)
      CRW2  = CRW (2)
      CRH2  = CRH (2)
      CWH2  = CWH (2)
      CRWH2 = CRWH(2)
C
      DC1   = DWL*CW1   - C2   + C1
      DC2   = DWL*CW2   - C2   + C1
      DCH1  = DWL*CWH1  - CH2  + CH1
      DCH2  = DWL*CWH2  - CH2  + CH1
      DCR1  = DWL*CRW1  - CR2  + CR1
      DCR2  = DWL*CRW2  - CR2  + CR1
CC    DCRH1 = DWL*CRWH1 - CRH2 + CRH1
CC    DCRH2 = DWL*CRWH2 - CRH2 + CRH1
C
C---- set  AINT, dAINT/dRL, dAINT/dHL
      AINT(IC) =  (1.0-TW)* C1   + TW* C2
     &         + ((1.0-TW)*DC1   - TW*DC2  )*(TW-TW*TW)
      AINT_RL  =  (1.0-TW)* CR1  + TW* CR2
     &         + ((1.0-TW)*DCR1  - TW*DCR2 )*(TW-TW*TW)
      AINT_HL  =  (1.0-TW)* CH1  + TW* CH2
     &         + ((1.0-TW)*DCH1  - TW*DCH2 )*(TW-TW*TW)
C
C---- also, the WL derivatives of the quantities above
      AINT_WL  = (C2   - C1
     &     + (1.0-4.0*TW+3.0*TW*TW)*DC1   + (3.0*TW-2.0)*TW*DC2  )/DWL
      AINTW_RL = (CR2  - CR1
     &     + (1.0-4.0*TW+3.0*TW*TW)*DCR1  + (3.0*TW-2.0)*TW*DCR2 )/DWL
      AINTW_HL = (CH2  - CH1
     &     + (1.0-4.0*TW+3.0*TW*TW)*DCH1  + (3.0*TW-2.0)*TW*DCH2 )/DWL
C
      AINTW_WL = ((6.0*TW-4.0)*DC1  + (6.0*TW-2.0)*DC2 )/DWL**2
C
C
C---- convert derivatives wrt to spline coordinates (RL,WL,HL) into 
C-    derivatives wrt input variables (Rtheta,f,H)
      AINT_R(IC) = (AINT_RL + 0.5*AINT_WL) / (AL10 * RSP)
      AINT_W(IC) = (AINT_WL              ) / (AL10 * WSP)
      AINT_H(IC) =  AINT_HL
C
      AINTW_R(IC) = (AINTW_RL + 0.5*AINTW_WL) / (AL10**2 * WSP*RSP)
      AINTW_W(IC) = (AINTW_WL - AL10*AINT_WL) / (AL10**2 * WSP*WSP)
      AINTW_H(IC) =  AINTW_HL                 / (AL10    * WSP    )
C
 1000 CONTINUE
C
      ALFR = AINT(1)
      ALFR_R = AINT_R(1)
      ALFR_W = AINT_W(1)
      ALFR_H = AINT_H(1)
      ALFRW_R = AINTW_R(1)
      ALFRW_W = AINTW_W(1)
      ALFRW_H = AINTW_H(1)
C
      ALFI = AINT(2)
      ALFI_R = AINT_R(2)
      ALFI_W = AINT_W(2)
      ALFI_H = AINT_H(2)
      ALFIW_R = AINTW_R(2)
      ALFIW_W = AINTW_W(2)
      ALFIW_H = AINTW_H(2)
C
C---- if we're within the spline data space, the derivatives are valid
      IF(OK) RETURN
C
C---- if not, the  ai  value is clamped, and its derivatives are zero
      ALFR_R = 0.0
      ALFR_W = 0.0
      ALFR_H = 0.0
      ALFRW_R = 0.0
      ALFRW_W = 0.0
      ALFRW_H = 0.0
C
      ALFI_R = 0.0
      ALFI_W = 0.0
      ALFI_H = 0.0
      ALFIW_R = 0.0
      ALFIW_W = 0.0
      ALFIW_H = 0.0
C
      RETURN
C
C--------------------------------------------------------
C---- pick up here if OS file not given
 800  CONTINUE
      WRITE(*,*)'OSMAP: Environment variable OSMAP not defined'
      WRITE(*,*)'       Must be set to Orr-Sommerfeld database filename'
C---- don't try again
      NOFILE = .TRUE.
      RETURN
C
C--------------------------------------------------------
C---- pick up here for file open error
 900  CONTINUE
      WRITE(*,*)
      WRITE(*,*)'OSMAP: Orr-Sommerfeld database file not found: ', 
     &           OSFILE(1:LOSF)
      WRITE(*,*)'       Will return zero amplification rates'
C---- don't try again
      NOFILE = .TRUE.
      OK = .FALSE.
C
      RETURN
      END ! OSMAP