Update documentation

Author: hyeoksu-lee

docs/documentation/case.md

@@ -455,7 +455,7 @@ The table lists velocity field parameters. The parameters are optionally used to
 
 - `vel_profile` activates setting the mean streamwise velocity to hyperbolic tangent profile. This option works only for 2D and 3D cases.
 
-- `instability_wave` activates the perturbation of initial velocity by instability waves obtained from linear stability analysis for a mixing layer with hyperbolic tangent mean streamwise velocity profile. This option only works for 2D and 3D cases, together with `vel_profile`=true.
+- `instability_wave` activates the perturbation of initial velocity by instability waves obtained from linear stability analysis for a mixing layer with hyperbolic tangent mean streamwise velocity profile. This option only works for 2D and 3D cases, together with `vel_profile`=TRUE.
 
 
 ## Enumerations