1D:SettingTheNumericalParameters

Setting Numerical Parameters

There are some parameters controlling the numerical aspects of the calculation:

• You must specify a suitable time step. A time step of one hour is adequate for most cases (the choice of time steps is further discussed in WUFI's Performance and Limitations).

• For special purposes, you may exclude either heat or moisture transport from the calculations.
  For example, you may thus easily determine the thermal transmittance of a wall with a complicated moisture distribution: specify the distribution as the initial moisture profile and prevent it from spreading by turning off moisture transport. Perform a calculation with constant climate, applying a suitable temperature gradient across the assembly until steady-state conditions are reached and analyse the resulting heat flow.

• You may also switch off capillary conduction only, in order to examine the importance of the remaining vapour diffusion.

• You may switch off latent heat effects (heat of fusion and/or heat of evaporation) to examine the extent to which they affect the results.
  

In case WUFI reports problems with the accuracy of the results, you should tune WUFI to stricter convergence criteria or stronger underrelaxation, sacrificing some calculation speed.

Possible numerical problems and countermeasures are further discussed in the on-line help for the dialog "Status of Last Calculation" and in WUFI's Performance and Limitations.