/[ascend]/trunk/models/johnpye/compressible_flow.a4c

Diff of /trunk/models/johnpye/compressible_flow.a4c

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-revision 2460 by jpye,
Mon Apr 18 14:39:32 2011 UTC
+revision 2461 by jpye,
Mon Apr 25 09:09:57 2011 UTC
 Line 61 
 END ideal_gas_node;
      Add cross-sectional area to the above model; not needed for normal shock
      calculations, but useful in nozzle calcs.
  *)
- MODEL ideal_gas_duct_node REFINES ideal_gas_node;
+ MODEL ideal_gas_duct_node;
+     (* we incorporate state as submodel so we can ARE_THE_SAME non-duct nodes *)
+     state IS_A ideal_gas_node;
+     M ALIASES state.M;
+     p ALIASES state.p;
+     T ALIASES state.T;
+     v ALIASES state.v;
+     rho ALIASES state.rho;
+     Vel ALIASES state.Vel;
+     MM ALIASES state.MM;
+     R ALIASES state.R;
+     k ALIASES state.k;
+     c ALIASES state.c;
      A IS_A area;
      mdot IS_A mass_rate;
      mdot = rho * A * Vel;
-Line 80 
 MODEL air_duct_node REFINES ideal_gas_du
+Line 93 
 MODEL air_duct_node REFINES ideal_gas_du
      k :== 1.4;
  END air_duct_node;
- (*-----------------------NORMAL SHOCK IN ISENTROPIC FLOW----------------------*)
- (*
-     Model of a stationary normal shock in air. Using a moving frame of
-     reference, it can be used to model a moving shock wave as well.
-     Equations from Potter & Wiggert, 3rd SI edition, sects 9.1, 9.2 and 9.4.
- *)
- MODEL air_normal_shock;
-     S1, S2 IS_A air_node;
-     k ALIASES S1.k;
-     S2.M^2 = ( S1.M^2 + 2/(k-1) ) / (2*k/(k-1)*S1.M^2 - 1);
-     S2.p / S1.p = 2*k/(k+1)*S1.M^2 - (k-1)/(k+1);
-     S2.T / S1.T = ( 1 + (k-1)/2*S1.M^2) * (2*k/(k-1)*S1.M^2 - 1)/ ((k+1)^2/2/(k-1)*S1.M^2);
- END air_normal_shock;
- (*------------------------------EXAMPLE MODELS -------------------------------*)
- (*
-     This model reproduces the results of Example 9.5 from Potter & Wiggert,
-rd SI edition. The question asks to determine the pressure and temperature
-     conditions downstream of a shock wave passing through ambient air of given
-     state.
-     Tested, works OK -- JP
- *)
- MODEL example_potter_wiggert_ex_9_5 REFINES air_normal_shock;
- METHODS
- METHOD on_load;
-     FIX S1.Vel, S1.p, S1.T;
-     S1.Vel := 450 {m/s};
-     S1.p := 80 {kPa};
-     S1.T := 15 {K} + 273.15 {K};
- END on_load;
- END example_potter_wiggert_ex_9_5;
- (*
-     This model reproduces the results of Example 9.5 from Potter & Wiggert,
-rd SI edition. This problem shows the wind speeds implicit behind a strong
-     shock wave such as that arising from a high-powered bomb explosions.
-     Although the problem as given in P&W can be solved even without doing so,
-     we have added an assumption that the ambient air pressure is 101.3 kPa. This
-     allows the model to be 'square' and the pressure and temperature behind the
-     shock wave (4.83 bar, 500 K) to also be calculated.
-     Tested, works OK -- JP
- *)
- MODEL example_potter_wiggert_ex_9_6 REFINES air_normal_shock;
-     Vel_induced IS_A speed;
-     Vel_induced = S2.Vel - S1.Vel;
- METHODS
- METHOD on_load;
-     FIX S1.Vel, S1.T, S1.p;
-     S1.Vel := 700 {m/s};
-     S1.T := 15 {K} + 273.15 {K};
-     S1.p := 101.3 {kPa};
- END on_load;
- END example_potter_wiggert_ex_9_6;
  (*----------------------------STAGNATION CONDITIONS---------------------------*)
-Line 237 
 METHOD on_load;
+Line 186 
 METHOD on_load;
  END on_load;
  END example_potter_wiggert_ex_9_2;
  (*
+     Potter & Wiggert 3rd SI ed, Example 9.3.
      Converging-diverging nozzle with exit 40 cm² and throat 10 cm², with flow
      coming from reservoir at 20 °C, 500 kPa. Two different exit pressures can
      result in M = 1 at the throat -- we calculate what those pressure are.
-     Potter & Wiggert 3rd SI ed, Example 9.3.
      For this problem, saturation states are the upstream reservoir, and we
      assert that A_star is the throat area and A is the exit area. These areas
-Line 277 
 METHOD on_load;
+Line 227 
 METHOD on_load;
  END on_load;
  END example_potter_wiggert_ex_9_3;
+ (*-----------------------NORMAL SHOCK IN ISENTROPIC FLOW----------------------*)
+ (*
+     Model of a stationary normal shock in air. Using a moving frame of
+     reference, it can be used to model a moving shock wave as well.
+     Equations from Potter & Wiggert, 3rd SI edition, sects 9.1, 9.2 and 9.4.
+ *)
+ MODEL air_normal_shock;
+     S1, S2 IS_A air_node;
+     k ALIASES S1.k;
+     S2.M^2 = ( S1.M^2 + 2/(k-1) ) / (2*k/(k-1)*S1.M^2 - 1);
+     S2.p / S1.p = 2*k/(k+1)*S1.M^2 - (k-1)/(k+1);
+     S2.T / S1.T = ( 1 + (k-1)/2*S1.M^2) * (2*k/(k-1)*S1.M^2 - 1)/ ((k+1)^2/2/(k-1)*S1.M^2);
+ END air_normal_shock;
+ MODEL air_duct_normal_shock;
+     S1, S2 IS_A air_duct_node;
+     shock IS_A air_normal_shock;
+     S1.state, shock.S1 ARE_THE_SAME;
+     S2.state, shock.S2 ARE_THE_SAME;
+     S1.A, S2.A ARE_THE_SAME;
+ END air_duct_normal_shock;
+ (*------------------------------EXAMPLE MODELS -------------------------------*)
+ (*
+     This model reproduces the results of Example 9.5 from Potter & Wiggert,
+rd SI edition. The question asks to determine the pressure and temperature
+     conditions downstream of a shock wave passing through ambient air of given
+     state.
+     Tested, works OK -- JP
+ *)
+ MODEL example_potter_wiggert_ex_9_5 REFINES air_normal_shock;
+ METHODS
+ METHOD on_load;
+     FIX S1.Vel, S1.p, S1.T;
+     S1.Vel := 450 {m/s};
+     S1.p := 80 {kPa};
+     S1.T := 15 {K} + 273.15 {K};
+ END on_load;
+ END example_potter_wiggert_ex_9_5;
+ (*
+     This model reproduces the results of Example 9.5 from Potter & Wiggert,
+rd SI edition. This problem shows the wind speeds implicit behind a strong
+     shock wave such as that arising from a high-powered bomb explosions.
+     Although the problem as given in P&W can be solved even without doing so,
+     we have added an assumption that the ambient air pressure is 101.3 kPa. This
+     allows the model to be 'square' and the pressure and temperature behind the
+     shock wave (4.83 bar, 500 K) to also be calculated.
+     Tested, works OK -- JP
+ *)
+ MODEL example_potter_wiggert_ex_9_6 REFINES air_normal_shock;
+     Vel_induced IS_A speed;
+     Vel_induced = S2.Vel - S1.Vel;
+ METHODS
+ METHOD on_load;
+     FIX S1.Vel, S1.T, S1.p;
+     S1.Vel := 700 {m/s};
+     S1.T := 15 {K} + 273.15 {K};
+     S1.p := 101.3 {kPa};
+ END on_load;
+ END example_potter_wiggert_ex_9_6;
+ (*
+     This model reproduces the results of Example 9.7 from Potter & Wiggert,
+rd SI edition. The problem relates to the calculation of outlet conditions
+     and flow rate for a converging-diverging nozzle, given specified upstream
+     reservoir pressure and temperature, given the throat and exit areas, and
+     subject to the fact that there is a normal shock at the nozzle's exit plane.
+     For a shock to exist at the exit, we know that we must have M = 1 at the
+     throat, so A* = A_t.
+ *)
+ MODEL example_potter_wiggert_ex_9_7;
+     noz IS_A isentropic_stagnation;
+     A_star ALIASES noz.A_star;
+     A ALIASES noz.A;
+     p_0 ALIASES noz.p_0;
+     T_0 ALIASES noz.T_0;
+     shock IS_A air_duct_normal_shock;
+     shock.S1, noz.flow ARE_THE_SAME;
+     rec IS_A isentropic_stagnation;
+     rec.flow, shock.S2 ARE_THE_SAME;
+     p_2 ALIASES rec.p;
+     mdot ALIASES noz.mdot;
+ METHODS
+ METHOD on_load;
+     FIX A_star, A;
+     A_star := 5 {cm^2};
+     A := 10 {cm^2};
+     FIX p_0, T_0;
+     p_0 := 90 {kPa};
+     T_0 := 20 {K} + 273.15 {K};
+ END on_load;
+ END example_potter_wiggert_ex_9_7;

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