# TYPE=ORIFICE CD1 or just TYPE=ORIFICE: Cd = 1 **URL:** \ **Category:** Uncategorized\ **Created:** [December 14, 2023, 12:33pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976 "2023-12-14T12:33:28Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [December 14, 2023, 12:33pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/1 "2023-12-14T12:33:28Z")
Hi, I’m in need to compute an orifice dimension in a network to induce a desired pressure lost in the line. I’m finding very helpful Mr.kraska example linearnet.inp which I’m using as reference, but I have some doubts. I’m posting the file itself which I have follow in detail with my notes on it . Most of my initial doubts have been clear now with the assistance of the ccx manual but I still need some help. I have add some ?¿? at those points I have a doubt. Thanks in advance. ```auto ** ** Structure: gas network. ** Test objective: orifice element, flux given. ** **Node zero that is later used is not defined. *NODE,NSET=NALL 1, 1, 0, 0 2, 2, 0, 0 3, 3, 0, 0 4, 4, 0, 0 5, 5, 0, 0 6, 6, 0, 0 7, 7, 0, 0 **Seems the test uses two consecutive Orifice elements. *ELEMENT, TYPE=D,ELSET=EGAS 2, 2, 3, 4 3, 4, 5, 6 *ELEMENT, TYPE=D,ELSET=EIO ** a dummy network entrance element expressing that liquid is entering the ** network (element 1). It is characterized by a node number 0 as first node. 1, 0, 1, 2 ** a dummy network exit element expressing that liquid is leaving the network (element 4) 4, 6, 7, 0 ** First and last node is the same (node number 0) meaning Closed loop system. Should I expect results at entrance and exit to be the same.?¿? **That was not in the Example file. Isn't ABSOLUTE ZERO=0 and others like conductivity definition will be required if heat transfer is involved. **PHYSICAL CONSTANTS,ABSOLUTE ZERO=0. *MATERIAL,NAME=GAS ** Originally DOUBLE PRECISION. Pending to check later if needed. *FLUID CONSTANTS 0.1002353938E+4, 0.1711000000E-04, 0.27315E+03 0.1002353938E+4, 0.1949281697E-04, 0.32315E+03 0.1002353938E+4, 0.2169996934E-04, 0.37315E+03 0.1002353938E+4, 0.2376071192E-04, 0.42315E+03 0.1002353938E+4, 0.2569766947E-04, 0.47315E+03 0.1002353938E+4, 0.2752859550E-04, 0.52315E+03 0.1002353938E+4, 0.2926763423E-04, 0.57315E+03 0.1002353938E+4, 0.3092621879E-04, 0.62315E+03 0.1002353938E+4, 0.3251371525E-04, 0.67315E+03 0.1002353938E+4, 0.3403789021E-04, 0.72315E+03 0.1002353938E+4, 0.3550525531E-04, 0.77315E+03 0.1002353938E+4, 0.3692132461E-04, 0.82315E+03 0.1002353938E+4, 0.3829080968E-04, 0.87315E+03 0.1002353938E+4, 0.3961776952E-04, 0.92315E+03 0.1002353938E+4, 0.4090572698E-04, 0.97315E+03 0.1002353938E+4, 0.4215776043E-04, 0.10231E+04 0.1002353938E+4, 0.4337657658E-04, 0.10732E+04 0.1002353938E+4, 0.4456456897E-04, 0.11232E+04 0.1002353938E+4, 0.4572386531E-04, 0.11732E+04 0.1002353938E+4, 0.4685636617E-04, 0.12232E+04 **That was not in the original example file.Not mandatory without heat transfers. **CONDUCTIVITY,TYPE=ISO **24.34,373. **44.5,573. ** [m2/K s2] units seems involved *SPECIFIC GAS CONSTANT 287. **Type=Orifice (Only Area =A seems required) What are those last parameters.page 142 ccx 2.21 manual ?¿? *FLUID SECTION,ELSET=EGAS,TYPE=ORIFICE,MATERIAL=GAS 3.1415e-4,.2e-1,.4e-1 *FLUID SECTION,ELSET=EIO,TYPE=INOUT,MATERIAL=GAS **TYPE=TOTAL. PRESSURE on side nodes. *INITIAL CONDITIONS, TYPE=TOTAL PRESSURE 6,0.06e6 4,0.07e6 **Isn't inhomogeneous boundary conditions imposed inside the step block.?¿? **Mass flow rate goes to midside node degree of freedom 1. **Temperature goes to side nodes degree of freedom 0. **Pressure goes to side nodes like temperature degree of freedom 2 *BOUNDARY,MASS FLOW 1,1,1,0.03 **BOUNDARY **Isn't needed here an exclusive *BOUNDARY card for temperatures and pressures ?¿? **temperatures 2,0,0,500 6,0,00,500 **Pressures 2,2,2,0.08e6 **Is there a Steady state solution for this problem ?¿?. **Reducing initial time step to 0.1 doesn't solve and give error. *STEP,INC=100 *HEAT TRANSFER,STEADY STATE,SOLVER=PARDISO 1.,1. *NODE FILE PT,TT *NODE PRINT,NSET=NALL U,NT *END STEP ``` ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [December 14, 2023, 6:35pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/2 "2023-12-14T18:35:52Z")
Any idea what those constants mean. They don’t seem to be right acording to the manual considering Cd=1 for TYPE=ORIFICE.? ```auto *FLUID SECTION,ELSET=EGAS,TYPE=ORIFICE,MATERIAL=GAS 3.1415e-4,.2e-1,.4e-1 ``` The orifice element is characterized by the following constants (to be speci- fied in that order on the line beneath the \*FLUID SECTION card): • the cross section A. • the orifice diameter d (not needed for Cd = 1). • the length L (not needed for Cd = 1). • the inlet corner radius r (mutually exclusive with α; not needed for Cd =1). • Cthe inlet corner angle α in ◦ (mutually exclusive with r; not needed for Cd = 1). • the orifice-to-upstream pipe diameter ratio β = d/D (only for TYPE=ORIFICE PK MS). • the rotational velocity v, if the orifice is part of a rotating structure (not needed for Cd = 1). • a reference network element (not needed for Cd = 1). ---
**Author:** ![fgr](https://avatars.discourse-cdn.com/v4/letter/f/f4b2a3/32.png) [@fgr](https://calculix.discourse.group/u/fgr)\ **Post date:** [December 14, 2023, 8:32pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/3 "2023-12-14T20:32:47Z")
@Disla , I doesn’t really have it present, but when Cd = 1 or very closed to 1 and only the cross section area is needed, then I would consider it more like an aperture in a photo objective than an orifice. So the other way around when the length is infinitely small, then will Cd also be 1 or close to 1, and corner will be infinitely sharp. I cannot image other than the upstream pipe diameter ratio also should be needed, but in fact I don’t know how this TYPE=ORIFICE PK MS should look like since I can’t find it in the manual. It will probably require a look in some of the references. In fact I could risk to be more confused than you. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [December 15, 2023, 7:10am UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/4 "2023-12-15T07:10:25Z")
Thank you fgr. I planned to start with the simplest option and from a given example before moving to another orifice more elaborated. I have solved the problem by other means by the moment but there is a big potential to explode those network elements if I manage to understand them better. This time has been too precipitated. Let’s see if I find some more examples out there. Thank you again. 👍 ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [December 15, 2023, 12:41pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/5 "2023-12-15T12:41:30Z")
> [@Disla](#): > > I have solved the problem by other means How ? Using hand calcs or regular CFD ? That’s how I would approach such problems in most cases. Fluid elements in CalculiX are quite specific. They are closer to Simscape/Simulink than to typical FEA. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [December 15, 2023, 8:39pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/6 "2023-12-15T20:39:13Z")
One can calculate pressure drops of gases with the same formula as liquids if the relative change of density is low (change of density/density \< 0.02) I 'm still interested to make it work and solve it in a more appropriate way. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [December 19, 2023, 10:33pm UTC](https://calculix.discourse.group/t/type-orifice-cd1-or-just-type-orifice-cd-1/1976/7 "2023-12-19T22:33:24Z")
Why are Mass Flow , Total pressure and Temperature shown under the displacements and velocitiy tags? It’s really confusing. displacements (vx,vy,vz) for set NALL and time 0.1000000E+01 ``` 1 1.290000E+01 0.000000E+00 0.000000E+00 2 1.290000E+01 7.391503E+04 3.430000E+02 3 1.290000E+01 0.000000E+00 0.000000E+00 4 1.290000E+01 0.000000E+00 3.430000E+02 5 1.290000E+01 0.000000E+00 0.000000E+00 ```