Add emitter backflow option

Adds a global hydraulic option to allow backflow or not through emitter elements. To maintain backward compatibility the default is YES.

include/epanet.cs

@@ -182,6 +182,8 @@ namespace EpanetCSharpLibrary
         public const int EN_WALLORDER = 20;
         public const int EN_TANKORDER = 21;
         public const int EN_CONCENLIMIT = 22;
+        public const int EN_DEMANDPATTERN = 23;
+        public const int EN_EMITBACKFLOW = 24;
 
         public const int EN_LOWLEVEL = 0;      //Control types
         public const int EN_HILEVEL = 1;

include/epanet2.bas

@@ -179,6 +179,8 @@ Public Const EN_BULKORDER = 19
 Public Const EN_WALLORDER = 20
 Public Const EN_TANKORDER = 21
 Public Const EN_CONCENLIMIT = 22
+Public Const EN_DEMANDPATTERN = 23
+Public Const EN_EMITBACKFLOW = 24
 
 Public Const EN_LOWLEVEL = 0      ' Control types
 Public Const EN_HILEVEL = 1

include/epanet2.pas

@@ -185,6 +185,8 @@ const
  EN_WALLORDER    = 20;
  EN_TANKORDER    = 21;
  EN_CONCENLIMIT  = 22;
+ EN_DEMANDPATTERN = 23;
+ EN_EMITBACKFLOW  = 24;
 
  EN_LOWLEVEL   = 0;   { Control types }
  EN_HILEVEL    = 1;

include/epanet2.vb

@@ -174,6 +174,8 @@ Public Const EN_BULKORDER = 19
 Public Const EN_WALLORDER = 20
 Public Const EN_TANKORDER = 21
 Public Const EN_CONCENLIMIT = 22 
+Public Const EN_DEMANDPATTERN = 23
+Public Const EN_EMITBACKFLOW = 24
 
 Public Const EN_LOWLEVEL = 0      ' Control types
 Public Const EN_HILEVEL = 1

include/epanet2_enums.h

@@ -9,7 +9,7 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 08/13/2022
+ Last Updated: 02/05/2023
  ******************************************************************************
 */
 
@@ -335,7 +335,8 @@ typedef enum {
   EN_WALLORDER      = 20, //!< Wall reaction order for pipes (either 0 or 1)
   EN_TANKORDER      = 21, //!< Bulk water reaction order for tanks
   EN_CONCENLIMIT    = 22, //!< Limiting concentration for growth reactions
-  EN_DEMANDPATTERN  = 23  //!< Name of default demand pattern
+  EN_DEMANDPATTERN  = 23, //!< Name of default demand pattern
+  EN_EMITBACKFLOW   = 24  //!< 1 if emitters can backflow, 0 if not
 } EN_Option;
 
 /// Simple control types

src/enumstxt.h

@@ -7,7 +7,7 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 08/13/2022
+ Last Updated: 02/05/2023
  ******************************************************************************
 */
 
@@ -112,6 +112,10 @@ char *RptFlagTxt[]      = {w_NO,
                            w_YES,
                            w_FULL};
                            
+char *BackflowTxt[]     = {w_NO,
+                           w_YES,
+                           NULL};
+
 char *SectTxt[]         = {s_TITLE,     s_JUNCTIONS, s_RESERVOIRS,
                            s_TANKS,     s_PIPES,     s_PUMPS,
                            s_VALVES,    s_CONTROLS,  s_RULES,

src/epanet.c

@@ -7,7 +7,7 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 08/13/2022
+ Last Updated: 02/05/2023
  ******************************************************************************
 */
 
@@ -1205,6 +1205,9 @@ int DLLEXPORT EN_getoption(EN_Project p, int option, double *value)
     case EN_DEMANDPATTERN:
         v = hyd->DefPat;
         break;
+    case EN_EMITBACKFLOW:
+        v = hyd->EmitBackFlag;
+        break;
     default:
         return 251;
     }
@@ -1367,6 +1370,11 @@ int DLLEXPORT EN_setoption(EN_Project p, int option, double value)
         hyd->DefPat = pat;
         break;
 
+    case EN_EMITBACKFLOW:
+        if (value == 0.0 || value == 1.0) hyd->EmitBackFlag = (int)value;
+        else return 213;
+        break;
+
     default:
         return 251;
     }

src/hydcoeffs.c

@@ -7,7 +7,7 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 08/13/2022
+ Last Updated: 02/05/2023
  ******************************************************************************
 */
 
@@ -495,6 +495,13 @@ void emitterheadloss(Project *pr, int i, double *hloss, double *hgrad)
 
     // Otherwise use normal emitter head loss function
     else *hloss = (*hgrad) * q / hyd->Qexp;
+    
+    // Prevent negative flow if backflow not allowed
+    if (hyd->EmitBackFlag == 0 && q <= 0.0)
+    {
+        *hgrad += CBIG;
+        *hloss += CBIG * q;
+    }
 }
 
 

src/inpfile.c

@@ -7,7 +7,7 @@ Description:  saves network data to an EPANET formatted text file
 Authors:      see AUTHORS
 Copyright:    see AUTHORS
 License:      see LICENSE
-Last Updated: 08/13/2022
+Last Updated: 02/05/2023
 ******************************************************************************
 */
 
@@ -33,6 +33,7 @@ extern char *MixTxt[];
 extern char *TstatTxt[];
 extern char *RptFlagTxt[];
 extern char *SectTxt[];
+extern char *BackflowTxt[];
 
 void saveauxdata(Project *pr, FILE *f)
 /*
@@ -676,6 +677,7 @@ int saveinpfile(Project *pr, const char *fname)
         fprintf(f, "\n PATTERN             %s", net->Pattern[hyd->DefPat].ID);
     fprintf(f, "\n DEMAND MULTIPLIER   %-.4f", hyd->Dmult);
     fprintf(f, "\n EMITTER EXPONENT    %-.4f", 1.0 / hyd->Qexp);
+    fprintf(f, "\n EMITTER BACKFLOW    %s", BackflowTxt[hyd->EmitBackFlag]);
     fprintf(f, "\n VISCOSITY           %-.6f", hyd->Viscos / VISCOS);
     fprintf(f, "\n DIFFUSIVITY         %-.6f", qual->Diffus / DIFFUS);
     fprintf(f, "\n SPECIFIC GRAVITY    %-.6f", hyd->SpGrav);

src/input1.c

@@ -7,7 +7,7 @@ Description:  retrieves network data from an EPANET input file
 Authors:      see AUTHORS
 Copyright:    see AUTHORS
 License:      see LICENSE
-Last Updated: 07/08/2019
+Last Updated: 02/05/2023
 ******************************************************************************
 */
 
@@ -120,6 +120,7 @@ void setdefaults(Project *pr)
     hyd->Epump = EPUMP;         // Default pump efficiency
     hyd->Emax = 0.0;            // Zero peak energy usage
     hyd->Qexp = 2.0;            // Flow exponent for emitters
+    hyd->EmitBackFlag = 1;      // Allow emitter backflow
     hyd->DefPat = 0;            // Default demand pattern index
     hyd->Dmult = 1.0;           // Demand multiplier
     hyd->RQtol = RQTOL;         // Default hydraulics parameters

src/input3.c

@@ -7,7 +7,7 @@ Description:  parses network data from a line of an EPANET input file
 Authors:      see AUTHORS
 Copyright:    see AUTHORS
 License:      see LICENSE
-Last Updated: 08/13/2022
+Last Updated: 02/05/2023
 ******************************************************************************
 */
 
@@ -25,6 +25,7 @@ Last Updated: 08/13/2022
 extern char *MixTxt[];
 extern char *Fldname[];
 extern char *DemandModelTxt[];
+extern char *BackflowTxt[];
 
 // Exported functions
 int powercurve(double, double, double, double, double, double *, double *,
@@ -1759,6 +1760,7 @@ int optionchoice(Project *pr, int n)
 **    UNBALANCED          STOP/CONTINUE {Niter}
 **    PATTERN             id
 **    DEMAND MODEL        DDA/PDA
+**    EMITTER BACKFLOW    YES/NO
 **--------------------------------------------------------------
 */
 {
@@ -1897,6 +1899,16 @@ int optionchoice(Project *pr, int n)
         hyd->DemandModel = choice;
     }
     
+    // EMITTER BACKFLOW
+    else if (match(parser->Tok[0], w_EMITTER))
+    {
+        if (n < 2) return 0;
+        if (!match(parser->Tok[1], w_BACKFLOW)) return -1;
+        choice = findmatch(parser->Tok[2], BackflowTxt);
+        if (choice < 0) return setError(parser, 2, 213);
+        hyd->EmitBackFlag = choice;
+    }
+
     // Return -1 if keyword did not match any option
     else return -1;
     return 0;

src/text.h

@@ -7,7 +7,7 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 08/13/2022
+ Last Updated: 02/05/2023
  ******************************************************************************
 */
 
@@ -131,6 +131,7 @@
 #define   w_SEGMENTS    "SEGM"
 #define   w_TOLERANCE   "TOLER"
 #define   w_EMITTER     "EMIT"
+#define   w_BACKFLOW    "BACK"
 
 #define   w_PRICE       "PRICE"
 #define   w_DMNDCHARGE  "DEMAN"

src/types.h

@@ -7,7 +7,7 @@
  Authors:      see AUTHORS
  Copyright:    see AUTHORS
  License:      see LICENSE
- Last Updated: 08/13/2022
+ Last Updated: 02/05/2023
  ******************************************************************************
 */
 
@@ -744,6 +744,7 @@ typedef struct {
     Epat,                  // Energy cost time pattern
     DemandModel,           // Fixed or pressure dependent
     Formflag,              // Head loss formula flag
+    EmitBackFlag,          // Emitter backflow flag
     Iterations,            // Number of hydraulic trials taken
     MaxIter,               // Max. hydraulic trials allowed
     ExtraIter,             // Extra hydraulic trials