Problem with NIntegrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg127769] Problem with NIntegrate*From*: maves <vesel.mateja at gmail.com>*Date*: Mon, 20 Aug 2012 21:30:03 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Hello, I'm trying to numerically integrate a complicated expression and Mathematica keeps showing plenty of error messages, such as "NIntegrate::slwcon:Numerical integration converging too slowly; /.../", "NIntegrate::eincr: The global error of the strategy GlobalAdaptive has increased more than 2000 times./../" and so on. If I only want to see the spatial distribution of the solution (contour plots in different planes etc.) , it somehow manages to come to an end, but the problem is that I need to use this solution in NDSolve, so it would take too long for the program to find the root. One of the problematic integrals is for instance NIntegrate[ R (x - R Cos[\[Phi]] )/((x - R Cos[\[Phi]] )^2 + (y - R Sin[\[Phi]] )^2 + (0 - Z)^2)^(3/2), {\[Phi], 0, 2 Pi}, {R, b, b + c}, {Z, R - (b + c), -R + (b + c)} Any idea what is "wrong" with the integrand so that I get all these error messages?