COMMU1

This option is used to simulate chambered airbags and may be used to unfold an airbag.

Each COMMU1 type monitored volume works like an AIRBAG1 type monitored volume with possible vent communication with some other COMMU1 type monitored volume. A chambered airbag is therefore designed with two or more COMMU1 type monitored volumes.

Each monitored volume can have an inflator and vent holes.

Case 1: Folded Airbag

To model a folded airbag, one COMMU1 type monitored volume is used for each folded part. The boundary between two folded parts is closed with a void (dummy) property set. The area of communication is defined with this void property set. The pressure in each folded part will be different and the area of communication will increase during inflation. With this modelization the volume with inflator will inflate first and before the folded parts.
Volume 1: Prop. 1 + 4 + 5
Communication area: vol. 1 to 2: prop. 4
vol. 1 to 3: prop. 5
Volume 2: Prop. 2 + 4
Communication area: vol. 2 to 1: prop. 4
Volume 3: Prop. 3 + 5
Communication area: vol. 3 to 1: prop. 5
Figure 1.


Case 2: General Use

Monitored volume 1 can communicate with monitored volume 2 with or without communication from 2 to 1. Communication area, deflation pressure or time from 1 to 2 can be different than corresponding values from 2 to 1. That way it is possible to model a valve communication.

Two communication monitored volumes can have common nodes or common shell property set, but this is optional.

Volume 1 communicates with volume 2, and volume 2 with volume 1 and 3, but there is no communication from 3 to 2.
Figure 2.


General Equations

Same equations for AIRBAG1 type monitored volume are used, but incoming and outgoing enthalpy and kinetic energies will take into account the communicating bags. For each communicating volume for which pressure is lower than in current volume, a mass and energy flow is computed with same equations for vent holes, the external pressure is just replaced by the pressure of communicating volume:

u 2 = 2 γ γ 1 P ρ ( 1 ( P v e n t P ) γ 1 γ ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWG1bWaaW baaSqabeaacaaIYaaaaOGaeyypa0ZaaSaaaeaacaaIYaGaeq4SdCga baGaeq4SdCMaeyOeI0IaaGymaaaadaWcaaqaaiaadcfaaeaacqaHbp GCaaWaaeWaaeaacaaIXaGaeyOeI0YaaeWaaeaadaWcaaqaaiaadcfa daWgaaWcbaGaamODaiaadwgacaWGUbGaamiDaaqabaaakeaacaWGqb aaaaGaayjkaiaawMcaamaaCaaaleqabaWaaSaaaeaacqaHZoWzcqGH sislcaaIXaaabaGaeq4SdCgaaaaaaOGaayjkaiaawMcaaaaa@5171@
with,
P v e n t = max ( P c r i t , P n e i g h b o r ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGqbWaaS baaSqaaiaadAhacaWGLbGaamOBaiaadshaaeqaaOGaeyypa0JaciyB aiaacggacaGG4bWaaeWaaeaacaWGqbWaaSbaaSqaaiaadogacaWGYb GaamyAaiaadshaaeqaaOGaaiilaiaadcfadaWgaaWcbaGaamOBaiaa dwgacaWGPbGaam4zaiaadIgacaWGIbGaam4BaiaadkhaaeqaaaGcca GLOaGaayzkaaaaaa@4EA0@
ρ v e n t = ρ ( P v e n t P ) 1 γ MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaHbpGCda WgaaWcbaGaamODaiaadwgacaWGUbGaamiDaaqabaGccqGH9aqpcqaH bpGCdaqadaqaamaalaaabaGaamiuamaaBaaaleaacaWG2bGaamyzai aad6gacaWG0baabeaaaOqaaiaadcfaaaaacaGLOaGaayzkaaWaaSGa aeaacaaIXaaabaGaeq4SdCgaaaaa@48AA@
m ˙ o u t = ρ v e n t A v e n t u = ρ ( P e x t P ) 1 γ A v e n t u MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaaceWGTbGbai aadaWgaaWcbaGaam4BaiaadwhacaWG0baabeaakiabg2da9iabeg8a YnaaBaaaleaacaWG2bGaamyzaiaad6gacaWG0baabeaakiabgwSixl aadgeadaWgaaWcbaGaamODaiaadwgacaWGUbGaamiDaaqabaGccqGH flY1caWG1bGaeyypa0JaeqyWdi3aaeWaaeaadaWcaaqaaiaadcfada WgaaWcbaGaamyzaiaadIhacaWG0baabeaaaOqaaiaadcfaaaaacaGL OaGaayzkaaWaaWbaaSqabeaadaWcaaqaaiaaigdaaeaacqaHZoWzaa aaaOGaeyyXICTaamyqamaaBaaaleaacaWG2bGaamyzaiaad6gacaWG 0baabeaakiabgwSixlaadwhaaaa@61C2@
E ˙ o u t = m ˙ o u t E ρ V = ( P e x t P ) 1 γ A v e n t u E V MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaaceWGfbGbai aadaWgaaWcbaGaam4BaiaadwhacaWG0baabeaakiabg2da9iqad2ga gaGaamaaBaaaleaacaWGVbGaamyDaiaadshaaeqaaOWaaSaaaeaaca WGfbaabaGaeqyWdiNaamOvaaaacqGH9aqpdaqadaqaamaalaaabaGa amiuamaaBaaaleaacaWGLbGaamiEaiaadshaaeqaaaGcbaGaamiuaa aaaiaawIcacaGLPaaadaahaaWcbeqaamaalaaabaGaaGymaaqaaiab eo7aNbaaaaGccaWGbbWaaSbaaSqaaiaadAhacaWGLbGaamOBaiaads haaeqaaOGaamyDamaalaaabaGaamyraaqaaiaadAfaaaaaaa@5466@

These mass and energy fluxes are removed from current volume and added to communicating volume at the next cycle.

Inflator, Vent Hole, Initial Conditions

Inflator, atmospheric vent holes and initial conditions are identical to /MONVOL/AIRBAG1 type monitored volume.

Specific Input

The specific input for this type is:
μ
Viscosity factor
P e x t MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuamaaBa aaleaacaWGLbGaamiEaiaadshaaeqaaaaa@39D7@
External pressure
Δ P d e f MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqqHuoarci GGqbWaaSbaaSqaaiaadsgacaWGLbGaamOzaaqabaaaaa@3B85@
Relative vent deflation pressure
Avent
Vent area ( s u r f _ I D v = 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGZbGaam yDaiaadkhacaWGMbGaai4xaiaadMeacaWGebWaaSbaaSqaaiaadAha aeqaaOGaeyypa0JaaGimaaaa@3F9E@ ) or discharge factor ( s u r f _ I D v 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGZbGaam yDaiaadkhacaWGMbGaai4xaiaadMeacaWGebWaaSbaaSqaaiaadAha aeqaaOGaeyiyIKRaaGimaaaa@405F@ )
Tstart
Time to deflate vent hole

Initial gas and injected gas defined with /MAT/GAS.

Inject properties defined with /PROP/INJECT1 or /PROP/INJECT2.
fct_IDM
Injected mass curve (or mass rate)
FscaleM
Scale factor for injected mass curve (or mass rate)
fct_IDT
Injected temperature curve
FscaleT
Scale factor for injected temperature curve
sens_ID
Sensor number to start injection
Nvent
Number of vent hole
Nbag
Number of communicating volume
For each communicating volume (1 to Nbag):
bag_ID
Identification of communicating volume
s u r f _ I D c MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGZbGaam yDaiaadkhacaWGMbGaai4xaiaadMeacaWGebWaaSbaaSqaaiaadoga aeqaaaaa@3DC1@
Defines the communication area
Δ P C d e f MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqqHuoarci GGqbWaaSbaaSqaaiaadoeacaWGKbGaamyzaiaadAgaaeqaaaaa@3C4D@
Relative communication deflation pressure
Acom
Communication area ( s u r f _ I D c = 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGZbGaam yDaiaadkhacaWGMbGaai4xaiaadMeacaWGebWaaSbaaSqaaiaadAha aeqaaOGaeyypa0JaaGimaaaa@3F9E@ ) or discharge factor ( s u r f _ I D c 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGZbGaam yDaiaadkhacaWGMbGaai4xaiaadMeacaWGebWaaSbaaSqaaiaadoga aeqaaOGaeyiyIKRaaGimaaaa@404C@ )
Tcom
Time to deflate communication area

In volume j input, the data for communication with volume k concerns only the flow from j to k. The data concerning the flow from k to j is defined in volume k input.