Adaptation of friction and form losses

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Adaptation of friction and form losses

Dear developers, 

I would like to get some advice on how to properly set flow losses in Athlet. When I switch off the flow loss corrections (izeta0 = 0) the input file runs normally. As soon as I switch on the corrections, I am getting the following error:  (from the .out file)

VARIATION OF INPUT DATA DURING PRESSURE ITERATION:

#TFO ANAMO J JPRI INPUT DATA VARIED DATA INPUT DATA VARIED DATA VARIATION (%)

2 P1-HL 1 1 SDFJ = 3.95567D+01 5.60585D+00 ZFFJ = 4.82000D+01 6.83076D+00 -8.58283D+01

***** DG1CON: FATAL ERROR IN JUNCTION 1 ***** THE VARIATION OF ZETA NECESSARY FOR THE PRESSURE ITERATION IS > +100% OR -50% ! ***** PROGRAM STOP WILL OCCUR LATER ON!

This error is repeated many times throughout other nodes of the objects of primary circuit, but not in the secondary circuit. If I understood the manual correctly, the SDFJ value is derived from the object's geometry (if not input by user). This is confusing for me because any geometry or topology error would have been caught during the first steps of input data processing, however, the program seems to try to vary these data. I have tried experimenting with different values in Friction PW, but none of the changes seemed to influence the variation. Even blocking out (-*---) the whole friction PW does not help. I use the 3.1#02 version. 

Could you please point me in the right direction as to where should I look for the error? 

Thank you! 

Topology data: 

----- CHAIN01 @ PRIMARY LOOP NO. 1
@ IPRI0 ISYSO
1 1
@ SBO ANAMO SEO IARTO
0. 'R-UP-NU' 0. 1
0. 'P1-HL' 14.650 1
0. 'P1-SG-HCL' 0. 1
(other following objects cut out)

Object data: 

K---- P1-HL @ 1 LOOP HOT LEG
@ ITYPO FPARO ICMPO
20 1. 0
----- NETWORK
@ SNO1 NIO1
0. 10
14.650
----- JUNTYPES
@ STO JTYPO ATYPO
8.820 3 'V-MVHL-P1'
----- GEOMETRY
@ SG0 Z0 D0 A0 V0 DEP0
0.000 10.120 0.496 0. 0. 0.
1.645 10.120 0.496 0. 0. 0.
4.445 8.720 0.496 0. 0. 0.
13.170 8.720 0.496 0. 0. 0.
13.390 8.940 0.496 0. 0. 0.
13.650 9.200 0.496 0. 0. 0.
13.820 9.370 0.495 0. 0. 0.
14.060 9.610 0.495 0. 0. 0.
14.200 9.750 0.800 0. 0. 0.
@ 14.450 10.000 0.800 0. 0. 0.
14.650 10.200 0.800 0. 0. 0.
----- FRICTION
@zvysenie hodnot ani vynulovanie nic nepomohlo
@ ITPMO ALAMO ROUO
2 0.03 20.E-6 @ 
@ SF0 SDFJO ZFFJO ZFBJO
0.00 0. 48.2 25.96 @ LOOP INLET
1.645 0. 37.5 1.4 @ 30 DEG BEND
4.445 0. 37.5 1.4 @ 30 DEG BEND
10.949 0. 23.8 0.891 @ 19 DEG BEND
13.170 0. 165.8 6.19 @ 90 DEG BEND
14.650 0. 315.5 4.12 @ DIFFUSER
----- DRIFT
@ S01 JFLOO JDRIFT
0.  2  1
----- INITCOND
@ SIO PO TO GO QO ICKOO
0.0 %PS-P% 295. %RPV-F%/6 0. 0
@

Athlet-Admin

Hello,

Thank you for this question!

During Steady State Calculation, ATHLET tries to establish a consistent state for your complete model based on the usually incomplete (and sometimes even inconsistent) data provided. One measure is the adaptation of junction pressure losses.

As far as I understand, you provided as first priority chain (PC) a closed loop through your primary system via hot leg 1 (P1-HL). Since it is a closed loop, pressure losses and pressure increases (pump head) along the loop have to cancel out to achieve steady state conditions. Thus, ATHLET increases or decreases the (usually not exactly known) pressure losses for every (!) junction of the respective PC by the same factor. Both friction and form losses are likewise corrected. In your case, these corrections are off limits. Thus, the simulation is stopped.

What you should do now: Check the major pressure differences along this PC for correctness and plausibility with regard to specification. Important parameters are typically pump head, friction and form losses (e.g. DPFRLJ), momentum flux term (e.g. DPMFLJ). Significant contributions by form loss AND momentum flux should be existent for internals such as the lower core plate, for the hot/cold leg nozzle region, etc. They are printed in the .out-file.

Best regards,

Philipp Schöffel