# Order of boundary conditions in a Partial Differential Equation

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 August 2, 2010, 15:28 Order of boundary conditions in a Partial Differential Equation #1 New Member   Gaurav Join Date: Aug 2010 Location: London Posts: 5 Rep Power: 15 Is it mathematically incorrect to have a 3rd order boundary condition for a 2nd order Partial Differential Equation?

 August 2, 2010, 16:50 #2 Senior Member   Join Date: Jul 2009 Posts: 357 Rep Power: 18 I assume you are referring to a condition on the third derivative of the function to be solved for - in that case the answer is yes - it is incorrect. You would specify conditions on the function or the derivative of the function (or a mixture). The differential equation itself only defines the nth derivative of the function, so n+1 order derivative information on the boundaries is really meaningless. If you are referring to the order of accuracy of a discretization scheme, then the statement makes sense mathematically, since you could have a third-order accurate approximation to a first-derivative. But it may or may not adversely interact with the 2nd-order approximation of the interior scheme. gaurav_bhutani likes this.

 May 6, 2015, 16:19 #3 New Member   Gaurav Join Date: Aug 2010 Location: London Posts: 5 Rep Power: 15 Thanks a lot for the explanation.

 Tags boundary conditions, mathematics, pde