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Merge pull request #1327 from JoePfeiffer/fix-1325

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set pressure drag to 0 and flag a warning if tube inner radius is 0
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Joe Pfeiffer 2022-05-04 10:31:35 -06:00 committed by GitHub
commit 1a66d46b61
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3 changed files with 12 additions and 3 deletions
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1
core/resources/l10n/messages.properties
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@ -1759,6 +1759,7 @@ Warning.ZERO_RADIUS_BODY = Zero length bodies may not result in accurate simulat
Warning.TUBE_STABILITY = Tube fin stability calculations may not be accurate.
Warning.TUBE_SEPARATION = Space between tube fins may not result in accurate simulations.
Warning.TUBE_OVERLAP = Overlapping tube fins may not result in accurate simulations.
Warning.ZERO_INNER_RADIUS = Tube with inner radius 0 may not result in accurate simulations.
! Scale dialog
ScaleDialog.lbl.scaleRocket = Entire rocket

1
core/src/net/sf/openrocket/aerodynamics/Warning.java
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@ -395,4 +395,5 @@ public abstract class Warning {
public static final Warning TUBE_STABILITY = new Other(trans.get("Warning.TUBE_STABILITY"));
public static final Warning TUBE_SEPARATION = new Other(trans.get("Warning.TUBE_SEPARATION"));
public static final Warning TUBE_OVERLAP = new Other(trans.get("Warning.TUBE_OVERLAP"));
public static final Warning ZERO_INNER_RADIUS = new Other(trans.get("Warning.ZERO_INNER_RADIUS"));
}

13
core/src/net/sf/openrocket/aerodynamics/barrowman/TubeCalc.java
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@ -1,6 +1,7 @@
package net.sf.openrocket.aerodynamics.barrowman;
import net.sf.openrocket.aerodynamics.FlightConditions;
import net.sf.openrocket.aerodynamics.Warning;
import net.sf.openrocket.aerodynamics.WarningSet;
import net.sf.openrocket.rocketcomponent.RocketComponent;
import net.sf.openrocket.rocketcomponent.Tube;
@ -34,10 +35,16 @@ public abstract class TubeCalc extends RocketComponentCalc {
// Volume flow rate
final double Q = conditions.getVelocity() * refArea;
// pressure drop
final double deltap = 1.6 * Math.pow(Q, 1.85) * length /
// pressure drop.
final double deltap;
if (refArea == 0) {
warnings.add(Warning.ZERO_INNER_RADIUS);
deltap = 0;
} else {
deltap = 1.6 * Math.pow(Q, 1.85) * length /
(Math.pow(diameter, 5) * conditions.getAtmosphericConditions().getPressure());
}
// convert to CD and return
return deltap * refArea / conditions.getRefArea();
}