A correction method for shallow-water effects on ship speed trials - The Raven shallow-water correction
Date1 Jun 2022
In July 2021, the 29th ITTC conference accepted a new procedure to correct ship speed trials results for the effect of shallow water, under the name ‘Raven shallow water correction’. Adoption of this procedure was proposed by the ITTC Specialist Committee on Operation of Ships at Sea [ITTC 2021a]. The same correction method is also included in the 2022/2023 revision of ISO15016 “Guidelines for the assessment of speed and power performance by analysis of speed trial data”.
In view of the expected widespread use of this correction procedure, it is essential that its meaning, background, limitations and possible refinements are clear and generally accessible. This was not the case for the procedure previously used, Lackenby’s formula; and in my view, this has led to possible misunderstanding of that formula and its validity.
The present report aims to collect all information available now, including the steps taken to develop and validate the procedure. It collects the main information from several previous papers by the present author; adds several new checks and comparisons; and discusses all validations done and that could be found in the literature. The report is being sent to those we know are involved, and is also freely downloadable from the MARIN website.
The report is set up as follows. Chapter 2 discusses some previously proposed methods. Chapter 3 briefly lists the steps taken towards the present method, in chronological order. Then in Chapter 4 the different studies are discussed in detail. These texts are mostly a reworked and extended version of earlier publications and reports, backed up by some additional calculations.
Chapter 5 describes the correction algorithm, including the later extensions to make it self-contained, as asked by the ITTC SoS committee. Chapter 6 describes all validation material known to me: the full- scale trial data performed by MARIN, some older published data, comparisons with CFD made by others, and some other tests. Chapter 7 summarises the main points.
We hope this report will contribute to the usefulness of the method and may inspire further refinement.
In view of the expected widespread use of this correction procedure, it is essential that its meaning, background, limitations and possible refinements are clear and generally accessible. This was not the case for the procedure previously used, Lackenby’s formula; and in my view, this has led to possible misunderstanding of that formula and its validity.
The present report aims to collect all information available now, including the steps taken to develop and validate the procedure. It collects the main information from several previous papers by the present author; adds several new checks and comparisons; and discusses all validations done and that could be found in the literature. The report is being sent to those we know are involved, and is also freely downloadable from the MARIN website.
The report is set up as follows. Chapter 2 discusses some previously proposed methods. Chapter 3 briefly lists the steps taken towards the present method, in chronological order. Then in Chapter 4 the different studies are discussed in detail. These texts are mostly a reworked and extended version of earlier publications and reports, backed up by some additional calculations.
Chapter 5 describes the correction algorithm, including the later extensions to make it self-contained, as asked by the ITTC SoS committee. Chapter 6 describes all validation material known to me: the full- scale trial data performed by MARIN, some older published data, comparisons with CFD made by others, and some other tests. Chapter 7 summarises the main points.
We hope this report will contribute to the usefulness of the method and may inspire further refinement.
Contact
Arie de Jager
Senior Project Manager
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Tags
shallow waterresistance and propulsionspeed trials