From e965fa0751952596fc982c6dfb463bec955b9976 Mon Sep 17 00:00:00 2001
From: Elias Pipping <elias.pipping@fu-berlin.de>
Date: Tue, 22 Nov 2011 14:43:36 +0100
Subject: [PATCH] Compute second derivative (ignored)
---
dune/tectonic/nicefunction.hh | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/dune/tectonic/nicefunction.hh b/dune/tectonic/nicefunction.hh
index fdcdc0e4..6ff57720 100644
--- a/dune/tectonic/nicefunction.hh
+++ b/dune/tectonic/nicefunction.hh
@@ -73,6 +73,20 @@ class RuinaFunction : public NiceFunction {
return coefficient * normalStress * (a * std::log(eta * s) + mu);
}
+ /*
+ d/dx a * log(eta x) + mu
+ = a * 1/(eta x) * eta
+ = a/x
+ */
+ double virtual second_deriv(double s) const {
+ if (eta * s < rho)
+ return 0;
+ else if (eta * s == rho)
+ return 37; // TODO: not differentiable;
+ else
+ return coefficient * normalStress * (a / s);
+ }
+
private:
double coefficient;
double a;
--
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