OrcaFlex Validation

We publish a number of documents describing the validation of OrcaFlex. The principal of these is 99/005 OrcaFlex QA, Testing and Validation (263 KB) which describes the overall software QA process we use for developing OrcaFlex. The document also presents some comparisons of OrcaFlex with both real world data and other programs. We recommend that you read this document first.

Detailed Validation cases

We also publish a number of more detailed validation cases:

99/101 (95 KB)		A comparison with Flexcom for a typical deepwater SCR. The comparison covered statics, regular wave dynamics and irregular wave dynamics.
99/102 (120 KB)		A comparison with published results from a paper published at OMAE 2006. The paper compares OrcaFlex to a code written as part of the author's PhD study. Static and dynamic comparisons are considered.
99/103 (103 KB)		A comparison with published results from a paper published at OMAE 2005. The paper compares OrcaFlex to a solution of the governing set of continuous equations for a cable with bending stiffness for a static case.This comparison is a particularly strong validation of OrcaFlex since the authors use the continuous equations rather than the discretised finite element approach of OrcaFlex.
99/104 (164 KB)		A comparison with published work by Reismann, in the International Journal of Non-Linear Mechanics. This paper considers numerical analysis of the large-deflection due to coupled torsion/bending of a weightless cantilever.
99/105 (145 KB)		Three separate comparisons with standard theoretical results: (1) the catenary equations, extended to allow for axial stretch; (2) natural frequencies of a beam; (3) deflection of a cantilever beam.
99/106 (107 KB)		A validation of OrcaFlex's implementation of frequency dependent added mass and damping for vessels. This compares results from the BMT frequency domain program NMIWAVE with OrcaFlex time domain results. The comparison also provides validation of OrcaFlex's handling of wave load RAOs.
99/107 (652 KB)		A validation of the way OrcaFlex handles buoyancy forces and pipe internal contents pressure effects, and the resulting effective tension and wall tension that OrcaFlex reports. OrcaFlex is compared against results presented in Nigel Barltrop's book Dynamics of Floating Structures: Volume 2.
99/108 (545 KB)		A comparison of statistical properties of maxima from OrcaFlex generated wave elevation time series with theoretical values based on the Rayleigh distribution.

VIV Validation

Orcina have been involved with several studies that compared the various OrcaFlex VIV Toolbox models against real-world measurements of VIV. We have documented these comparisons in the following documents:

R648#01#02 OrcaFlex VIV Validation Summary (158 KB) gives an overview and summarises the three comparison studies, which are individually documented in the following three reports.
R648#02#02 OrcaFlex VIV Comparison with Delft Model Tests (555 KB) reports comparisons against measurements made at model tank tests in the large flume at the Delft Hydraulics Laboratory.
R648#03#02 OrcaFlex VIV Comparison with Schiehallion Results (269 KB) reports comparisons against measurements of a real full-scale drilling riser in the Schiehallion field.
R648#04#02 OrcaFlex VIV Comparison with Deepstar Seneca Trials (612 KB) reports comparisons against measurements from DeepStar project experiments on Lake Seneca.

These documents can also be downloaded in a single ZIP file: R648 OrcaFlex VIV validation.zip (1.4 MB).

Orcina thanks BP, the Norwegian Deepwater Programme, the DeepStar project and Southampton University for access to the VIV measurements used in these comparison studies.