Characteristics of drag due to streamwise inhomogeneous roughness
Characteristics of drag due to streamwise inhomogeneous roughness
Characteristics of the skin friction due to streamwise inhomogeneous roughness are investigated by modeling it in a simplified manner using step changes in equivalent sand grain roughness height k
s, denoted as P (k
s = 81.25 μm), Q (k
s = 325.00 μm) and R (k
s = 568.75 μm). The selected k
s values represent the common ship-hull roughness, i.e., from light slime to about small calcareous fouling. RANS simulations are performed to study the friction characteristics of various rough surfaces formed by a trio-combination of P, Q and R roughnesses on flat plates with streamwise lengths of 30, 60, 120 and 240 m. The three combinations of roughnesses form either homogeneous (PPP, QQQ or RRR) or inhomogeneous (PQR, PRQ, QPR, etc.) rough walled turbulent boundary layer flow. A step change in roughness height results in a sudden change of the local skin friction coefficient in the form of overshoot or undershoot, followed by a relaxation where the inhomogeneous local skin friction is slowly returning to the homogeneous local one. The sequence of roughness arrangement in a streamwise inhomogeneous roughness pattern plays a key role in the resulting overall skin friction with value increasing in the following order: PQR < PRQ < QPR < QRP < RPQ < RQP. The similarity laws hold for both homogeneous and inhomogeneous rough surfaces.
Biofouling, Energy efficiency, Inhomogeneous roughness, RANS simulations, Similarity laws, Skin friction
Suastika, K
f8949583-64f0-4bad-9fea-72c331c08815
Hakim, M L
bb41938a-dc30-4fe8-8c43-d835fec8601c
Nugroho, B
b2ac9cc0-24f5-4652-bf55-eb2c4ee5a86a
Nasirudin, A
b0678f8c-6ae5-46ac-82ce-0e91522b7d3c
Utama, I K A P
ae72d50b-7977-4d9f-a912-352f3b7378ce
Monty, J P
cae94b74-92b6-43cc-b278-5604636e0b3e
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
1 March 2021
Suastika, K
f8949583-64f0-4bad-9fea-72c331c08815
Hakim, M L
bb41938a-dc30-4fe8-8c43-d835fec8601c
Nugroho, B
b2ac9cc0-24f5-4652-bf55-eb2c4ee5a86a
Nasirudin, A
b0678f8c-6ae5-46ac-82ce-0e91522b7d3c
Utama, I K A P
ae72d50b-7977-4d9f-a912-352f3b7378ce
Monty, J P
cae94b74-92b6-43cc-b278-5604636e0b3e
Ganapathisubramani, Bharathram
5e69099f-2f39-4fdd-8a85-3ac906827052
Suastika, K, Hakim, M L, Nugroho, B, Nasirudin, A, Utama, I K A P, Monty, J P and Ganapathisubramani, Bharathram
(2021)
Characteristics of drag due to streamwise inhomogeneous roughness.
Ocean Engineering, 223, [108632].
(doi:10.1016/j.oceaneng.2021.108632).
Abstract
Characteristics of the skin friction due to streamwise inhomogeneous roughness are investigated by modeling it in a simplified manner using step changes in equivalent sand grain roughness height k
s, denoted as P (k
s = 81.25 μm), Q (k
s = 325.00 μm) and R (k
s = 568.75 μm). The selected k
s values represent the common ship-hull roughness, i.e., from light slime to about small calcareous fouling. RANS simulations are performed to study the friction characteristics of various rough surfaces formed by a trio-combination of P, Q and R roughnesses on flat plates with streamwise lengths of 30, 60, 120 and 240 m. The three combinations of roughnesses form either homogeneous (PPP, QQQ or RRR) or inhomogeneous (PQR, PRQ, QPR, etc.) rough walled turbulent boundary layer flow. A step change in roughness height results in a sudden change of the local skin friction coefficient in the form of overshoot or undershoot, followed by a relaxation where the inhomogeneous local skin friction is slowly returning to the homogeneous local one. The sequence of roughness arrangement in a streamwise inhomogeneous roughness pattern plays a key role in the resulting overall skin friction with value increasing in the following order: PQR < PRQ < QPR < QRP < RPQ < RQP. The similarity laws hold for both homogeneous and inhomogeneous rough surfaces.
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suastika-et-al-rev_2_unmarked_latex
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Published date: 1 March 2021
Additional Information:
Funding Information:
This research project was supported by the Ministry of Research, Technology and Higher Education of the Republic of Indonesia under the World Class Professor 2019 Grant, in collaboration with the University of Melbourne, Australia , and the University of Southampton, UK , with Grant Contract No. T/42/D2.3/KK.04.05/2019. BG gratefully acknowledged the support from EPSRC (Grant Ref. No. EP/R034370/1 ).
Publisher Copyright:
© 2021 Elsevier Ltd
Keywords:
Biofouling, Energy efficiency, Inhomogeneous roughness, RANS simulations, Similarity laws, Skin friction
Identifiers
Local EPrints ID: 446172
URI: http://eprints.soton.ac.uk/id/eprint/446172
ISSN: 0029-8018
PURE UUID: 4fcd3598-f6dd-4550-9bdc-bffd6ea5aeb2
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Date deposited: 26 Jan 2021 17:30
Last modified: 17 Mar 2024 06:15
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Contributors
Author:
K Suastika
Author:
M L Hakim
Author:
B Nugroho
Author:
A Nasirudin
Author:
I K A P Utama
Author:
J P Monty
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