Update case.md

Author: anandrdbz

docs/documentation/case.md

@@ -373,10 +373,10 @@ The source plane is defined in the finite region of the domain: $x\in[-\infty,\i
 | `mu_v` †	     | Real 		|	Viscosity |
 | `k_v` †	       | Real 		|	Thermal conductivity |
 | `qbmm` 	       | Logical 		|	Quadrature by  method of moments|
-| `dist_type` 	       | Integer 		|	Joint PDF for bubble radius and velocity (only when qbmm is true)|
-| `sigR` 	       | Real 		|	Standard deviation for PDF of bubble radius (only when qbmm is true) |
-| `sigV` 	       | Real 		|	Standard deviation for PDF of bubble velocity (only when qbmm is true) |
-| `rhoRV`	       | Real 		|	Correlation coefficient for joint PDF of bubble radius and velocity (only when qbmm is true) |
+| `dist_type` 	       | Integer 		|	Joint probability density function for bubble radius and velocity (only when qbmm is true)|
+| `sigR` 	       | Real 		|	Standard deviation for probability density function of bubble radius (only when qbmm is true) |
+| `sigV` 	       | Real 		|	Standard deviation for probability density function of bubble velocity (only when qbmm is true) |
+| `rhoRV`	       | Real 		|	Correlation coefficient for joint probability density function of bubble radius and velocity (only when qbmm is true) |
 
 
 
@@ -395,6 +395,8 @@ This table lists the ensemble-averaged bubble model parameters.
 - `polytropic` activates polytropic gas compression in the bubble.
 When `polytropic` is set `False`, the gas compression is modeled as non-polytropic due to heat and mass transfer across the bubble wall with constant heat and mass transfer coefficients based on ([Preston et al., 2007](references.md#Preston07)).
 
+- `polydisperse` activates polydispersity in the bubble model by means of a probability density function (PDF) of the equiliibrium bubble radius. 
+
 - `thermal` specifies a model for heat transfer across the bubble interface by an integer from 1 through 3.
 `thermal` $=$ 1, 2, and 3 correspond to no heat transfer (adiabatic gas compression), isothermal heat transfer, and heat transfer with a constant heat transfer coefficient based on [Preston et al., 2007](references.md#Preston07), respectively.