DeepStar – High Reynolds Number Results

Background

DEEPSTAR (www.deepstar.org) have made available high Reynolds (Re) number data for Vortex-Induced Vibration (VIV) benchmarking purposes. DEEPSTAR is a JIP consisting of the following operator companies:

The high RE data comes from CTR 5402 and CTR 6402. The purpose of these CTRs was to assess the potential value of high RE data as a source of predicting the response of flexible marine risers. The work relating to CTR 5402 was conducted during 2001, and supplemental high RE data was acquired during 2003 and covered by CTR 6402.

Experimental Details

The high RE data was obtained by Oceanic Consulting Corporation at St. Johns, Newfoundland, Canada. The experiments were conducted in the IMD 200m wave/towing tank facility, and the specifications of which are provided below.

IMD Wave/Towing Tank Facility Specifications

Length

200m

Width

12m

Still Water Depth

7m

Tow Carriage Speed

10m/s

Max. Wave Height (regular waves)

1m

Max. Sig. Wave Height (irregular waves)

0.5m

Range of Wavelengths at 7m Depth

0.5m – 40m

Max. Wind Speed: 1m from fans

11m/s

Max. Wind Speed: 5m from fans

5m/s

RE Range

2×105 – 1×106

The experimental setup for the high RE tests are summarised in the table below.

Test Cylinder Characteristics

Cylinder Length [L]

6m

Cylinder Diameter [D]

0.325m

Depth of Cylinder During Towing

2m below surface

Cylinder Surface: Rough

Ks/D = 0.0025

Cylinder Surface: Intermediate Rough

Ks/D = 0.0008

Cylinder Surface: Straked (Rough Jacket)

Ks/D = 0.0025

Strake Height

0.25 D

Strake Pitch

16 D

Two different modes of operations were tested:

For the free vibration mode, the cylinder is mounted in between the ends of tow bars. The tow bars can be interchanged to allow the cylinder to oscillate in one or 2 degrees of freedom, namely the transverse and in-line directions. A schematic drawing of the towing frame and the cylinder (pipe dynamometer) is shown below.


In the free vibration mode, turbulence screens were also used to assess the effects of turbulence on a smooth cylinder. Two different screens were used (fine and course). The position of the fine screen, relative to the smooth cylinder, is shown below.


The position of the course screen, relative to the smooth cylinder, is shown below.


In the forced vibration mode, the cylinder is placed directly between supporting struts and the tow bars were removed. The supporting struts are excited by an actuator, and mono-chromatic (single frequency excitation) and bi-chromatic (double frequency excitation) were applied to the cylinder. A schematic of the cylinder position operating in this mode is shown below.


Experimental Results

The data for high RE testing are divided into 2 key categories:

  1. Detailed experimental results:

  1. Summary experimental results:

Within each of the above categories, the following sub-categories are used:

Data is presented in graphical format as well as tabular form.