Mobile QR Code QR CODE : Journal of the Korean Society of Civil Engineers

  1. ๊ฑด๊ตญ๋Œ€ํ•™๊ต ํ† ๋ชฉ๊ณตํ•™๊ณผ ๊ต์ˆ˜ (Konkuk University)
  2. ํ•œ๊ตญํ•ด์–‘๊ณผํ•™๊ธฐ์ˆ ์› ์—ฐ๊ตฌ์› (Korea Institute of Ocean Science & Technology)
  3. ํ•œ๊ตญํ•ด์–‘๊ณผํ•™๊ธฐ์ˆ ์› ์„ ์ž„์—ฐ๊ตฌ์› (Korea Institute of Ocean Science & Technology)


๊ณต๊ทน๋งค์ฒด, Navier-Stokes ๋ฐฉ์ •์‹, Boussinesq ๋ฐฉ์ •์‹, ๊ณต๊ทน๋ฐฉํŒŒ์ œ, ๊ฐ€์ƒ์งˆ๋Ÿ‰๊ณ„์ˆ˜, ๋ฐ˜์‚ฌ์œจ, ํˆฌ๊ณผ์œจ
Porous media, Navier-Stokes equation, Boussinesq equation, Porous breakwater, Virtual mass coefficient, Reflection coefficient, Transmission coefficient

  • 1. ์„œ ๋ก 

  • 2. ๊ณต๊ทน๋งค์ฒด Navier-Stokes ๋ฐฉ์ •์‹์˜ ์œ ๋„ ๋ฐ ๊ฒ€ํ† 

  • 3. ๊ณต๊ทน๋งค์ฒด์—์„œ์˜ Boussinesq ๋ฐฉ์ •์‹์˜ ์œ ๋„ ๋ฐ ์ ์šฉ

  •   3.1 Boussinesq ๋ฐฉ์ •์‹์˜ ์œ ๋„

  •   3.2 ์ง๋ฆฝ์‹ ๊ณต๊ทน ๋ฐฉํŒŒ์ œ์— ๋Œ€ํ•œ ์ ์šฉ

  • 4. ๊ฒฐ ๋ก 

1. ์„œ ๋ก 

์ผ๋ฐ˜์ ์ธ ์‚ฌ์„๋ฐฉํŒŒ์ œ ๋˜๋Š” ์‚ฌ์„ํ˜ธ์•ˆ์€ ์ œ์ฒด๋‚ด๋ถ€๊ฐ€ ๊ณต๊ทน๋งค์ฒด๋กœ ์ด๋ฃจ์–ด์ ธ ์žˆ์œผ๋ฉฐ ์ž…์‚ฌํŒŒ ์—๋„ˆ์ง€๊ฐ€ ์ œ์ฒด๋‚ด๋กœ ์นจํˆฌํ•˜์—ฌ ๋‚ด๋ถ€์—์„œ ๋ฐ˜์‚ฌ, ํˆฌ๊ณผ ๋˜๋Š” ์†Œ๋ฉธ๋˜๋Š” ํŠน์ง•์„ ๊ฐ–๋Š”๋‹ค. ๋”ฐ๋ผ์„œ, ์‚ฌ์„๊ตฌ์กฐ๋ฌผ์˜ ์„ฑ๋Šฅ์„ ์ •ํ™•ํžˆ ํŒŒ์•…ํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ์ œ์ฒด์˜ ์™ธ๋ถ€๋ฟ๋งŒ ์•„๋‹ˆ๋ผ ๊ณต๊ทน๋งค์ฒด ๋‚ด๋ถ€์—์„œ์˜ ํŒŒ๋™์žฅ์„ ๋™์‹œ์— ํ•ด์„ํ•˜์—ฌ์•ผ ํ•œ๋‹ค.

๊ณต๊ทน๋งค์ฒด๋‚ด์—์„œ์˜ ํŒŒ๋™์žฅ ํ•ด์„์„ ์œ„ํ•ด์„œ๋Š” ๋ฌผ๊ณผ ํ† ๋ฆฝ์ž์˜ ํ˜ผํ•ฉ์˜์—ญ์—์„œ์˜ ์ง€๋ฐฐ๋ฐฉ์ •์‹ ๋ฐ ๊ฒฝ๊ณ„์กฐ๊ฑด๋“ค์„ ๋จผ์ € ๊ฒ€ํ† ํ•˜์—ฌ์•ผ ํ•œ๋‹ค. ์‚ฌ์‹ค ์ƒ ๊ณต๊ทน๋งค์ฒด๋ฅผ ํ•˜๋‚˜์˜ ์—ฐ์†์ฒด๋กœ ๊ณ ๋ คํ•˜์—ฌ ์ผ์ข…์˜ Navier- Stokes ๋ฐฉ์ •์‹(์ดํ•˜ N-S ๋ฐฉ์ •์‹์œผ๋กœ ์นญํ•จ)์„ ์ˆ˜๋ฆฝํ•˜๊ณ ์ž ํ•˜๋Š” ์‹œ๋„๋Š” ์—ญ์‚ฌ๊ฐ€ ๊ฝค ์˜ค๋ž˜ ๋˜์—ˆ์œผ๋ฉฐ Biot (1956), De Josselin de Jong (1956), Pride et al.(1992), Verruijt(1994)๊ฐ€ ๊ด€๋ จ์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•œ ๋ฐ” ์žˆ๋‹ค. ๊ณต๊ทน๋งค์ฒด์—์„œ์˜ ํŒŒ๋™์žฅ ํ•ด์„์„ ์œ„ํ•ด์„œ๋Š” Sollitt and Cross (1972)๊ฐ€ N-S ๋ฐฉ์ •์‹์— ๊ทผ๊ฑฐํ•˜์—ฌ ์‚ฌ์„๋ฐฉํŒŒ์ œ์˜ ๋ฐ˜์‚ฌ์™€ ํˆฌ๊ณผ๋ฅผ ์ด๋ก ์ ์œผ๋กœ ํ•ด์„ํ•˜๊ธฐ ์œ„ํ•œ ์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ๊ทธ ์ดํ›„ van Gent (1995) ์—ญ์‹œ ๊ณต๊ทน๋งค์ฒด๋‚ด์—์„œ์˜ N-S ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜์˜€์œผ๋ฉฐ VOF ๋ฐฉ๋ฒ•์„ ์ด์šฉํ•˜์—ฌ ์‚ฌ์„๋ฐฉํŒŒ์ œ์— ์ ์šฉํ•œ ๋ฐ” ์žˆ๋‹ค. Cruz et al. (1997)์€ ๊ณต๊ทน๋งค์ฒด๋‚ด์—์„œ์˜ Boussinesq ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜๊ณ  ์ด๋ฅผ ์ˆ˜์ค‘ ์ž ์ œ์˜ ์„ฑ๋Šฅ์„ ๊ฒ€ํ† ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, Lynett et al. (2000)์€ ์—ญ์‹œ ํ˜•ํƒœ๋Š” ๋‹ค๋ฅด๋‚˜ ์ผ์ข…์˜ Boussinesq ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜์—ฌ ๊ณ ๋ฆฝํŒŒ ์ž…์‚ฌ์— ๋Œ€ํ•œ ์‚ฌ์„๋ฐฉํŒŒ์ œ์˜ ์„ฑ๋Šฅ์„ ๊ฒ€ํ† ํ•œ ๋ฐ” ์žˆ๋‹ค. ํ•œํŽธ, Sakakiyama and Kajima (1992)๋Š” ๊ณต๊ทน๋งค์ฒด๋‚ด์˜ N-S ๋ฐฉ์ •์‹์„ ์ง์ ‘ ํ•ด์„ํ•˜๋Š” ์ผ์ข…์˜ RANS ๋ชจ๋ธ์„ ์ œ์‹œํ•˜์˜€์œผ๋ฉฐ ํ˜„์žฌ์˜ CADMAS-SURF ํ”„๋กœ๊ทธ๋žจ(CDIT, 2001)์˜ ๊ธฐ์ดˆ๋ฅผ ์ œ๊ณตํ•˜์˜€๋‹ค. ์ตœ๊ทผ์—” Hu et al. (2012)์ด dam-break ํŒŒ์™€ ๊ณต๊ทน์ฒด๊ฐ„์˜ ์ƒํ˜ธ์ž‘์šฉ์— ๋Œ€ํ•œ ์ˆ˜์น˜ํ•ด์„์„ ์ˆ˜ํ–‰ํ•˜์˜€์œผ๋ฉฐ ๊ตญ๋‚ด์—์„œ๋Š” ์ด์ฐฝํ›ˆยท๋ฐ•์„คํ™” (2011)๊ฐ€ ์™„๊ฒฝ์‚ฌ๋ฐฉ์ •์‹์„ ์ด์šฉํ•˜์—ฌ ํˆฌ์ˆ˜์ธต์—์„œ์˜ ๋ถˆ๊ทœ์น™ํŒŒ ์ „ํŒŒ๋ฅผ ๋ชจ์˜ํ•œ ๋ฐ” ์žˆ๋‹ค.

์ƒ๊ธฐ์™€ ๊ฐ™์ด ๊ณต๊ทน๋งค์ฒด๋‚ด์—์„œ์˜ ํŒŒ๋™์žฅ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๊ฐ€ ์ง€์†์ ์œผ๋กœ ์ˆ˜ํ–‰๋˜์–ด ์™”์Œ์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ๊ด€๋ จ ๋ฌธํ—Œ๋“ค์„ ๊ฒ€ํ† ํ•˜์—ฌ ๋ณด๋ฉด N-S ๋ฐฉ์ •์‹์— ๊ทผ๊ฑฐํ•œ ์ง€๋ฐฐ๋ฐฉ์ •์‹์„ ๊ตฌ์„ฑํ•˜๋Š” ๊ฐ ํ•ญ๋“ค์—์„œ ๊ณต๊ทน๋ฅ ์˜ ์ ์šฉ ํ˜•ํƒœ๊ฐ€ ๋‹ค์†Œ ๋‹ค๋ฆ„์„ ๋ฐœ๊ฒฌํ•  ์ˆ˜ ์žˆ๋‹ค. ์ผ๋ฐ˜์ ์ธ ๋ฌผ ์˜์—ญ์—์„œ์˜ ํŒŒ๋™์žฅ๊ณผ๋Š” ๋‹ฌ๋ฆฌ ๊ณต๊ทน๋งค์ฒด๋‚ด์—์„œ๋Š” ํ† ๋ฆฝ์ž์—์„œ์˜ ๋งˆ์ฐฐ๋ ฅ๊ณผ ๊ด€์„ฑ๋ ฅ์— ๋”ฐ๋ฅธ ๋ชจ๋ฉ˜ํ…€ ๊ตํ™˜, ์ฆ‰, ๊ณต๊ทน ํ•ญ๋ ฅ์ด ์ „์ฒด์˜ ํŒŒ๋™์žฅ ๊ฒฐ์ •์— ์žˆ์–ด์„œ ๋งค์šฐ ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•œ๋‹ค. ๋”ฐ๋ผ์„œ, ์ง€๋ฐฐ๋ฐฉ์ •์‹์—์„œ ๊ฐ ํ•ญ๋“ค์˜ ๋น„๊ต์—์„œ ๊ณต๊ทน ํ•ญ๋ ฅ์˜ ์ƒ๋Œ€์  ํฌ๊ธฐ๊ฐ€ ์ž˜๋ชป ์„ค์ •๋  ๊ฒฝ์šฐ ๊ณ„์‚ฐ๊ฒฐ๊ณผ๊ฐ€ ํ˜„๊ฒฉํžˆ ๋‹ค๋ฅด๊ฒŒ ๋‚˜ํƒ€๋‚  ์ˆ˜ ์žˆ๋‹ค.

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์—ฐ์† ๊ณต๊ทน๋งค์ฒด ๋‚ด์— ๋ฏธ์†Œ๋ถ€ํ”ผ์˜ ๊ฒ€์‚ฌ์ฒด์ ์„ ์„ค์ •ํ•˜๊ณ  Reynolds ์ด์†ก์ •๋ฆฌ๋ฅผ ์ ์šฉํ•˜์—ฌ ์งˆ๋Ÿ‰๊ณผ ๋ชจ๋ฉ˜ํ…€์˜ ๊ตํ™˜์„ ๊ณ ๋ คํ•˜๋Š” ์ „ํ†ต์ ์ธ ๋ฐฉ๋ฒ•์— ๋”ฐ๋ผ N-S ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜๊ณ  ์ด๋ฅผ ๊ธฐ์กด ๋ฌธํ—Œ๋“ค์—์„œ์˜ ์‹๋“ค๊ณผ ๋น„๊ตํ•˜์˜€๋‹ค. ๊ทธ๋ฆฌ๊ณ  ์œ ๋„๋œ N-S ๋ฐฉ์ •์‹ ๋ฐ ๊ฒฝ๊ณ„์กฐ๊ฑด๋“ค์„ ์ด์šฉํ•˜์—ฌ ๊ณต๊ทน๋งค์ฒด๋‚ด์˜ Boussinesq ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜์˜€์œผ๋ฉฐ ์ด์ฐจ์› ์ง๋ฆฝ์‚ฌ์„ ๋ฐฉํŒŒ์ œ์— ๋Œ€ํ•˜์—ฌ ์ˆ˜์น˜ํ•ด์„์„ ์ˆ˜ํ–‰ํ•˜๊ณ  ์ด ๊ฒฐ๊ณผ๋ฅผ ๊ธฐ์กด์˜ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ๋“ค๊ณผ ๋น„๊ตํ•˜์˜€๋‹ค.

2. ๊ณต๊ทน๋งค์ฒด Navier-Stokes ๋ฐฉ์ •์‹์˜ ์œ ๋„ ๋ฐ ๊ฒ€ํ† 

Fig. 1์—์„œ ๋ณด์ด๋Š” ๋ฐ”์™€ ๊ฐ™์ด ๊ณต๊ทน๋ฅ (porosity)์ด PICAFC4.gif์ธ ๋“ฑ๋ฐฉ์„ฑ ๊ณต๊ทน๋งค์ฒด๋กœ ์ถฉ์ง„๋˜์–ด ์žˆ์œผ๋ฉฐ ์ฒด์ ๊ณผ ์งˆ๋Ÿ‰์ด ๊ฐ๊ฐ PICB16B.gif์™€ PICB17C.gifPICB19C.gif์ธ ๊ณ ์ •๋œ ๋ฏธ์†Œ๊ฒ€์‚ฌ์ฒด์ ์—์„œ์˜ ์ž„์˜ ์Šค์นผ๋ผ ๋˜๋Š” ๋ฒกํ„ฐ์— ๋Œ€ํ•˜์—ฌ Reynolds ์ด์†ก์ •๋ฆฌ๋ฅผ ์ ์šฉํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

KSCE_35_5_05_F1.jpg

Fig. 1. Infinitesimal Control Volume in Porous Media

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(1)

์—ฌ๊ธฐ์„œ, PICB23A.gif๋Š” ๊ฒ€์‚ฌํ‘œ๋ฉด, PICB24B.gif๋Š” ์ž„์˜ ์‹œ๊ฐ„์— PICB24C.gif์— ์กด์žฌํ•˜๋Š” ์ž„์˜ ์‹œ์Šคํ…œ(์งˆ๋Ÿ‰, ๋ชจ๋ฉ˜ํŠธ, ์—๋„ˆ์ง€ ๋“ฑ), PICB27C.gif๋Š” ๋‹จ์œ„์งˆ๋Ÿ‰๋‹น ์‹œ์Šคํ…œ(PICB2AC.gif), PICB2CC.gif๋Š” ๋‹จ์œ„ ์™ธํ–ฅ๋ฒ•์„ ๋ฒกํ„ฐ, PICB30B.gif๋Š” ์นจํˆฌ์œ ์†(Seepage velocity) ๋ฒกํ„ฐ๋ฅผ ๊ฐ๊ฐ ์˜๋ฏธํ•œ๋‹ค.

Eq. (1)์—์„œ ์œ ์ฒดํ๋ฆ„์˜ ์—ฐ์†๋ฐฉ์ •์‹๊ณผ ์šด๋™๋ฐฉ์ •์‹์€ ๊ฐ๊ฐ ์งˆ๋Ÿ‰(PICB30C.gif)๊ณผ ๋ชจ๋ฉ˜ํ…€(PICB31D.gif)์˜ ์ด์†ก์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ง๊ฐ์ขŒํ‘œ๊ณ„(์—ฐ์ง์ƒํ–ฅ +PICB32E.gif)์—์„œ ๋น„์••์ถ•์„ฑ ํ๋ฆ„์˜ ๊ฒฝ์šฐ์— ์ด๋“ค ๋ฐฉ์ •์‹์„ ์ง€ํ‘œ(Index)ํ˜•ํƒœ๋กœ ํ‘œํ˜„ํ•˜๋ฉด

PICB34E.gif; PICB35E.gif       (2)

PICB44A.gif ;

PICB45A.gif       (3)

์™€ ๊ฐ™๋‹ค. ์—ฌ๊ธฐ์„œ, PICB46B.gif๋Š” ์ฐจ๋ก€๋กœ PICB47C.gif์ถ•์„ ์˜๋ฏธํ•œ๋‹ค. Eq. (3)์˜ ์šฐ์ธก ํ•ญ๋“ค์€ ์ฐจ๋ก€๋Œ€๋กœ PICB47D.gif์— ๊ฐ€ํ•ด์ง€๋Š” ํ‘œ๋ฉด๋ ฅ(์••๋ ฅ+์ ์„ฑ๋งˆ์ฐฐ๋ ฅ), ์ž์ฒด ์ค‘๋ ฅ, ๊ณต๊ทน์ฒด ์ž…์ž์— ์˜ํ•œ ๋‚ด๋ถ€๋งˆ์ฐฐ๋ ฅ(Forchheimer ์‹), ๊ทธ๋ฆฌ๊ณ  ๊ณต๊ทน์ฒด ์ž…์ž์— ์ž‘์šฉํ•˜๋Š” ๊ด€์„ฑ๋ ฅ์„ ์˜๋ฏธํ•˜๋ฉฐ ๊ฐ๊ฐ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

PICB50A.gif (4)

PICB53A.gif (5)

PICB589.gif (6)

PICB646.gif (7)

Eq. (4)์—์„œ PICB656.gif๋Š” ์ ์„ฑ๊ณ„์ˆ˜, (5)์—์„œ PICB667.gif๋Š” ์ค‘๋ ฅ๊ฐ€์†๋„ ์„ฑ๋ถ„ PICB6A7.gif์„ ์˜๋ฏธํ•œ๋‹ค. Eq. (6)์—์„œ PICB6C7.gif, PICB6D7.gif๋Š” Forchheimer ์‹์—์„œ์˜ ๊ณต๊ทน์œจ๊ณผ ํ† ๋ฆฝ์ž ์ž…๊ฒฝ์— ์˜์กดํ•˜๋Š” ์œ ์ฐจ์› ํŒŒ๋ผ๋ฏธํ„ฐ๋“ค์ด๋‹ค(๋‹จ์œ„๋Š” ๊ฐ๊ฐ [PICB717.gif], [PICB860.gif] ์ž„). Eq. (7)์—์„œ PICB861.gif์€ ๊ฐ€์ƒ์งˆ๋Ÿ‰๊ณ„์ˆ˜๋ฅผ ์˜๋ฏธํ•˜๋ฉฐ ๋ถ€๊ฐ€์งˆ๋Ÿ‰๊ณ„์ˆ˜ PICB872.gif์™€ PICB8A2.gif์˜ ๊ด€๊ณ„๊ฐ€ ์žˆ๋‹ค. Eq. (6)์—์„œ PICB8B2.gif๋Š” Darcy ์œ ์†์œผ๋กœ์„œ ์นจํˆฌ์œ ์† PICB8C3.gif์™€๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๊ด€๊ณ„๊ฐ€ ์žˆ๋‹ค.

PICB8D3.gif (8)

Eqs. (4)~(7)์„ Eq. (3)์— ๋Œ€์ž…ํ•˜๋ฉด, ์ตœ์ข…์ ์œผ๋กœ ๊ณต๊ทน๋งค์ฒด์— ๋Œ€ํ•œ ์šด๋™๋ฐฉ์ •์‹์„

PICB923.gif (9)

PICB991.gif

์™€ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค. ์—ฌ๊ธฐ์„œ, PICB9B1.gif, PICB9D1.gif, PICB9E2.gif์ด๋ฉฐ

PICBA02.gif (10)

์ด๋‹ค. Eq. (9)๋ฅผ Darcy ์œ ์† PICBA13.gif๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ๋‹ค์‹œ ์“ฐ๋ฉด ๋‹ค์Œ ์‹๊ณผ ๊ฐ™๋‹ค.

PICBA91.gif (11)

PICBB1F.gif

Eq. (11)์—์„œ ์ •์ƒ ์ธต๋ฅ˜ ๊ฐ€์ • ํ•˜์— ๊ฐ€์†๋„ํ•ญ๊ณผ ๋‚ด๋ถ€๋งˆ์ฐฐ๋ ฅ ํ•ญ์„ ๋ฌด์‹œํ•˜๊ณ  ๊ณต๊ทน๋งˆ์ฐฐ๋ ฅ์—์„œ ์ธต๋ฅ˜ํ•ญ๋งŒ์„ ๊ณ ๋ คํ•˜๋ฉด

PICBB6E.gif ๋˜๋Š” PICBBBD.gif  (12)

์ด ๋˜์–ด ๊ฒฐ๊ตญ Darcy์˜ ๋ฒ•์น™๊ณผ ์ผ์น˜ํ•˜๊ฒŒ ๋œ๋‹ค.

๊ณต๊ทน๋งˆ์ฐฐ์— ๋Œ€ํ•œ Eq. (11)์—์„œ์˜ ๊ณ„์ˆ˜๋Š”

PICBBCD.gif, PICBBFD.gif    (13)

์™€ ๊ฐ™๋‹ค(๋‹จ์œ„๋Š” ๊ฐ๊ฐ [PICBC0E.gif], [PICBC1F.gif] ์ž„). ์—ฌ๊ธฐ์„œ, PICBC3F.gif๋Š” ๊ณ ์œ ํˆฌ์ˆ˜์„ฑ (Intrinsic permeability), PICBC40.gif๋Š” ๊ณต๊ทน ๋‚ด ํ๋ฆ„ ํ†ต๋กœ์˜ ํ˜•์ƒ์— ๊ด€๊ณ„๋˜๋Š” ๋ฌด์ฐจ์›์ˆ˜๋ฅผ ์˜๋ฏธํ•˜๋ฉฐ ํ†ต์ƒ 0.6์˜ ๊ฐ’์„ ๊ฐ–๋Š”๋‹ค. Fair and Hatch (1933)๋Š” ๊ณ ์œ ํˆฌ์ˆ˜์„ฑ์„ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ œ์‹œํ•˜์˜€๋‹ค.

PICBC8F.gif (14)

์—ฌ๊ธฐ์„œ, PICBCA0.gif5.0, PICBCB0.gif7.7์ด๋ฉฐ PICBCC1.gif์€ ๊ณต๊ทน๋งค์ฒด์˜ ํ‰๊ท ์ง๊ฒฝ์ด๋‹ค. ํ•œํŽธ, Engelund (1953)๋Š” Eq. (13)์˜ PICBCD1.gif, PICBCD2.gif๋ฅผ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ œ์‹œํ•˜์˜€๋‹ค.

PICBD02.gif (15)

PICBD13.gif (16)

Eqs. (15) and (16)์—์„œ PICBD24.gif= 780~1500 ๋˜๋Š” ๊ทธ ์ด์ƒ, PICBD34.gif = 1.8~3.6 ๋˜๋Š” ๊ทธ ์ด์ƒ์ด๋‹ค.

์šด๋™๋ฐฉ์ •์‹ (9)์™€ ํ•จ๊ป˜ ๊ธฐ์กด์˜ ํƒ€ ์—ฐ๊ตฌ๋“ค์—์„œ ์‚ฌ์šฉ๋œ ์‹ ๋“ค์„ Table 1์— ์ œ์‹œํ•˜์˜€๋‹ค. ๊ฐ ์‹์—์„œ ์œ ์†์€ ์นจํˆฌ์œ ์† PICBD45.gif๋กœ ํ†ต์ผํ•˜์˜€๋‹ค. Sollitt and Cross (1972)์˜ ์‹์€ ์ด๋ฅ˜๊ฐ€์†๋„ ํ•ญ์ด ๋น ์ ธ ์žˆ์œผ๋‚˜ Eq. (9)์™€ ๋™์ผํ•˜๋ฉฐ, Sakakiyama and Kajima (1992)์˜ ์‹๋„ ๋‚ด๋ถ€๋งˆ์ฐฐํ•ญ์ด ํ•ญ๋ ฅ๊ณ„์ˆ˜ PICBD55.gif๋กœ ํ‘œํ˜„๋œ ๊ฒƒ์„ ์ œ์™ธํ•˜๋ฉด ๋“ฑ๋ฐฉ์„ฑ ๋งค์ฒด์—์„œ PICBD66.gif์ด๋ฏ€๋กœ Eq. (9)์™€ ์ผ์น˜ํ•œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, Cruz et al. (1997)์˜ ์‹์€ ๊ฑฐ์˜ Eq. (9)์™€ ์œ ์‚ฌํ•œ ํ˜•ํƒœ๋ฅผ ๋ณด์ž„์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ์ขŒ๋ณ€์—์„œ ๊ณ„์ˆ˜ PICBD96.gif์— ๊ณต๊ทน๋ฅ ์ด ๊ณฑํ•ด์ ธ ์žˆ๋‹ค. ํ•œํŽธ, van Gent (1995)์˜ ์‹์—์„œ๋Š” Eq. (9)์™€ ๋น„๊ตํ•˜์—ฌ ์ด๋ฅ˜๊ฐ€์†๋„ํ•ญ์—์„œ ์ฐจ์ด๊ฐ€ ๋ฐœ๊ฒฌ๋˜๋ฉฐ ๋‚ด๋ถ€๋งˆ์ฐฐํ•ญ๋„ ๋‹ฌ๋ฆฌ ํ‘œํ˜„๋˜์–ด ์žˆ์Œ์„ ๋ณผ ์ˆ˜ ์žˆ๋‹ค.

Burcharth (1995)๋Š” ๊ด€์„ฑ๋ ฅํ•ญ๊ณผ ์••๋ ฅํ•ญ์˜ ๊ด€๊ณ„์— ๋Œ€ํ•œ ๊ณ ์ฐฐ์—์„œ Eq. (9)์˜ ํ˜•ํƒœ๋ณด๋‹ค๋Š” Cruz et al. ์‹์˜ ํ˜•ํƒœ๊ฐ€ ๋” ํ•ฉ๋‹นํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จํ•œ ๋ฐ” ์žˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, Cruz et al.์˜ ์‹์ด ์˜๋ฏธ๋ฅผ ๊ฐ–๊ธฐ ์œ„ํ•ด์„œ๋Š” Eqs. (4), (5) and (6)์—์„œ PICBDA7.gif๊ฐ€ ์•„๋‹Œ PICBDB7.gif๊ฐ€ ๋˜์–ด์•ผ ํ•œ๋‹ค. ์ด๋Š” Reynolds ์ด์†ก์ •๋ฆฌ๋ฅผ ์ด์šฉํ•œ ๋ณธ ์œ ๋„๊ณผ์ •์—์„œ ์•Œ ์ˆ˜ ์žˆ๋“ฏ์ด ์ „ํ˜€ ํƒ€๋‹นํ•˜์ง€ ์•Š๋‹ค. ๋‹ค๋งŒ, Cruz et al.์—์„œ์˜ ๊ณ„์ˆ˜ PICBDC8.gif๋ฅผ ๋˜ ๋‹ค๋ฅธ ๊ณ„์ˆ˜ PICBDF8.gif์œผ๋กœ ์น˜ํ™˜ํ•˜๋ฉด ํ˜•ํƒœ์ƒ์œผ๋กœ๋Š” Eq. (9)์™€ ๋™์ผํ•˜๊ฒŒ ๋œ๋‹ค. ์ด๋Š” Cruz et al.์˜ ์‹์ด ํƒ€๋‹น์„ฑ์„ ๊ฐ–๊ธฐ ์œ„ํ•ด์„œ๋Š” ๊ณ„์ˆ˜ PICBE18.gif์ด Eq. (10)์— ์˜ํ•˜์—ฌ ๊ฒฐ์ •๋˜๋Š” ์ด๋ก ์  ๊ณ„์ˆ˜๊ฐ€ ์•„๋‹ˆ๊ณ  ์ผ์ข…์˜ ์‹คํ—˜์ ์œผ๋กœ ๊ฒฐ์ •๋˜๋Š” ๊ณ„์ˆ˜๋ผ์•ผ ํ•œ๋‹ค. van Gent์˜ ์‹์—์„œ๋„ ๊ณ„์ˆ˜ PICBE29.gif๋Š” ์‹คํ—˜์  ์ƒ์ˆ˜ PICBE39.gif์— ์˜์กดํ•˜๋Š” ์ผ์ข…์˜ ์‹คํ—˜์  ๊ณ„์ˆ˜๋กœ ํ‘œํ˜„๋˜์–ด ์žˆ์œผ๋ฉฐ ๊ฐ€์ƒ์งˆ๋Ÿ‰๊ณ„์ˆ˜ PICBE4A.gif์ด ๋ถ€๊ฐ€์งˆ๋Ÿ‰๊ณ„์ˆ˜ PICBE5A.gif์™€ PICBE7B.gif์˜ ๊ด€๊ณ„๋กœ ์ธํ•˜์—ฌ 1๋ณด๋‹ค ํด ๊ฒƒ์ด๋ผ๋Š” ์˜ˆ์ƒ๊ณผ๋Š” ๋‹ฌ๋ฆฌ PICBE8B.gif์œผ๋กœ ์˜คํžˆ๋ ค 1๋ณด๋‹ค ์ž‘๊ฒŒ ๋‚˜ํƒ€๋‚˜ ์žˆ๋‹ค. Sakakiyama and Kajima (1992)๋„ ์—ญ์‹œ PICBEAC.gif๋ฅผ ์‹คํ—˜์ ์œผ๋กœ ๊ฒฐ์ •ํ•˜์—ฌ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ์ด์™€ ๊ฐ™์€ ์‚ฌ์‹ค์„ ์ข…ํ•ฉํ•ด๋ณผ ๋•Œ, ๊ณต๊ทน๋งค์ฒด ๋‚ด๋ถ€์—์„œ ํ† ๋ฆฝ์ž์— ์ž‘์šฉํ•˜๋Š” ๊ด€์„ฑ๋ ฅ์€ ๊ณ ๋ฆฝ๋œ ๋‹จ์ผ ์ž…๋ฐฉ์ฒด์— ์ž‘์šฉํ•˜๋Š” ๊ด€์„ฑ๋ ฅ๊ณผ๋Š” ๋งค์šฐ ๋‹ค๋ฅธ ์ž‘์šฉ ๋ฉ”์ปค๋‹ˆ์ฆ˜์„ ๊ฐ–๋Š” ๊ฒƒ์œผ๋กœ ๋ณด์ธ๋‹ค. ์ด์— ๋Œ€ํ•ด์„œ๋Š” ์ฐจํ›„ ์ˆ˜์น˜ํ•ด์„์—์„œ ๋‹ค์‹œ ๋…ผ์˜ํ•˜๊ธฐ๋กœ ํ•œ๋‹ค.

Table 1. Comparison of the Momentum Equations of Porous Media Flow

Existing researches

N-S Equations

Remarks

Equation (9)

PIC8505.gif

PIC8534.gif

PIC8564.gif ; PIC8575.gif

Sollitt and Cross (1972)

PIC85E3.gif

Sakakiyama and Kajima (1992)

PIC8690.gif

PIC86D0.gif

PIC8700.gif

PIC8710.gif = Surface permeability

Van Gent (1995)

PIC87DC.gif

PIC883B.gif ; PIC884C.gif

PIC88BA.gif; PIC88CB.gif

Cruz et al. (1997)

PIC89F5.gif

3. ๊ณต๊ทน๋งค์ฒด์—์„œ์˜ Boussinesq ๋ฐฉ์ •์‹์˜ ์œ ๋„ ๋ฐ ์ ์šฉ

3.1 Boussinesq ๋ฐฉ์ •์‹์˜ ์œ ๋„

Fig. 2์˜ ์ด์ฐจ์›(PICBEDB.gif ํ‰๋ฉด) ๊ณต๊ทน๋งค์ฒด ํŒŒ๋™์žฅ์— ๋น„์••์ถ•์„ฑ, ๋น„์ ์„ฑ์˜ ๊ฐ€์ •์„ ๋„์ž…ํ•˜๋ฉด ์—ฐ์†๋ฐฉ์ •์‹๊ณผ ์šด๋™๋ฐฉ์ •์‹์€ Eqs. (2) and (9)์—์„œ์˜ PICBEFC.gif์„ PICBF3B.gif๋กœ ์น˜ํ™˜ํ•˜์—ฌ Eqs. (17)~(19)์™€ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

KSCE_35_5_05_F2.jpg

Fig. 2. Coordinates of the 2D Wave Field Inside Porous Media

PICBF9A.gif (17)

PICC0F3.gif (18)

PICC20D.gif (19)

์—ฌ๊ธฐ์— ๋น„ํšŒ์ „ ์œ ์ฒดํ๋ฆ„์˜ ๊ฐ€์ •์„ ๋„์ž…ํ•˜๋ฉด,

PICC24C.gif (20)

์ด๋‹ค. Eqs. (17)~(20)์„ ํ’€๊ธฐ์œ„ํ•œ ๊ฒฝ๊ณ„์กฐ๊ฑด์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

- ์šด๋™ํ•™์  ์ž์œ ์ˆ˜๋ฉด ๊ฒฝ๊ณ„์กฐ๊ฑด

PICC2AB.gif on PICC2DB.gif  (21)

- ๋™์—ญํ•™์  ์ž์œ ์ˆ˜๋ฉด ๊ฒฝ๊ณ„์กฐ๊ฑด

PICC2EC.gif on PICC2FC.gif   (22)

- ๋ฐ”๋‹ฅ๊ฒฝ๊ณ„์กฐ๊ฑด

PICC33C.gif on PICC36C.gif      (23)

Boussinesq ๋ฐฉ์ •์‹์€ ํŒŒ๋™์˜ ์ง„ํญ PICC37C.gif, ๋Œ€ํ‘œ์ˆ˜์‹ฌ PICC38D.gif ๊ทธ๋ฆฌ๊ณ  ํŒŒ์žฅ PICC3AD.gif์‚ฌ์ด์˜ ๋‘๊ฐœ์˜ ๋ฌด์ฐจ์› ํŒŒ๋ผ๋ฏธํ„ฐ, ์ฆ‰ ๋น„์„ ํ˜•ํŒŒ๋ผ๋ฏธํ„ฐ PICC3CD.gif์™€ ์ฒœ์ˆ˜ํŒŒ๋ผ๋ฏธํ„ฐ PICC3EE.gif์— ๋Œ€ํ•˜์—ฌ Eqs. (17)~(23)์„ ์„ญ๋™์‹œ์ผœ ์ „๊ฐœํ•  ์ˆ˜ ์žˆ๋‹ค. ๋น„ ๊ณต๊ทน๋งค์ฒด ํ๋ฆ„์— ๋Œ€ํ•ด์„œ๋Š” Nwogu (1993)์™€ Wei et al. (1995)์ด ์†๋„ํฌํ…์…œ์„ ๋ฏธ์ง€์ˆ˜๋กœ ํ•˜๋Š” ์ง€๋ฐฐ๋ฐฉ์ •์‹์„ ์ด์šฉํ•˜์—ฌ Boussinesq ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•œ ๋ฐ” ์žˆ๋‹ค(Dingemans, 1997). ํ•œํŽธ, Walkley (1999)๋Š” ์ง์ ‘ Eqs. (17)~(19)์— ์ƒ์‘ํ•˜๋Š” ๋น„๊ณต๊ทน๋งค์ฒด์—์„œ์˜ ์ง€๋ฐฐ๋ฐฉ์ •์‹์„ ์ด์šฉํ•˜์—ฌ Peregrine (1972)์˜ ์‹๊ณผ Nwogu (1993)์˜ ํ™•์žฅํ˜• Boussinesq ์‹์„ ๊ฐ๊ฐ ์œ ๋„ํ•˜์˜€๋‹ค. ์ „์ž๋Š” ์ ์šฉ๋ฒ”์œ„๊ฐ€ ์ฒœํ•ดํŒŒ์— ๊ตญํ•œ๋˜๋Š” ๋ฐ˜๋ฉด, ํ›„์ž๋Š” ์ˆ˜์‹ฌ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ๋ถ„์‚ฐ์„ฑ์˜ ์žฌํ˜„์ •๋„๋ฅผ ์‹ฌํ•ดํŒŒ๋กœ ํ™•์žฅํ•œ ๊ฒƒ์ด๋‹ค.

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” Walkley (1999)์˜ ๋ฐฉ๋ฒ•์— ๋”ฐ๋ผ ๊ณต๊ทน๋งค์ฒด์— ๋Œ€ํ•œ Nwogu ํƒ€์ž…์˜ Boussinesq ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜๊ธฐ๋กœ ํ•œ๋‹ค. ๋จผ์ €, ํŒŒ๋ผ๋ฏธํ„ฐ PICC3EF.gif, PICC3FF.gif์™€ PICC400.gif๋ฅผ ์ด์šฉํ•˜์—ฌ Eqs. (17)~(23)์˜ ๋ชจ๋“  ์‹œ์Šคํ…œ ๋ณ€์ˆ˜๋“ค์„ ๋ฌด์ฐจ์›ํ™”ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICC430.gif, PICC450.gif, PICC461.gif, PICC481.gif, PICC4C1.gif

PICC52F.gif, PICC58E.gif, PICC5ED.gif

Boussinesq ๋ฐฉ์ •์‹์˜ ์Šค์ผ€์ผํ•ด์„์„ ์œ„ํ•˜์—ฌ PICC5FD.gif๊ณผ PICC62D.gif๋ฅผ ์ด์šฉํ•˜์—ฌ PICC62E.gif, PICC64E.gif, PICC64F.gif, PICC670.gif, PICC680.gif์˜ ์ž๋ฆฟ์ˆ˜๋ฅผ PICC6C0.gif์œผ๋กœ ์กฐ์ •ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICC6E0.gif, PICC73F.gif, PICC76F.gif,

PICC7ED.gif, PICC89A.gif

์ƒ๊ธฐ ๋ฌด์ฐจ์›์ˆ˜๋“ค์„ Eqs. (17)~(23)์— ๊ฐ๊ฐ ๋Œ€์ž…ํ•˜๋ฉด ๋‹ค์Œ์˜ Eqs. (24)~(30)์„ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

PICC918.gif (24)

PICCA03.gif (25)

PICCB0E.gif 

(26)

PICCB6C.gif (27)

PICCC19.gif (28)

PICCC68.gif (29)

PICCCD7.gif (30)

์—ฐ์†๋ฐฉ์ •์‹ (24)๋กœ ๋ถ€ํ„ฐ

PICCD07.gif (31)

์ด๋ฉฐ Eq. (27)์— ๋Œ€์ž…ํ•˜๋ฉด

PICCD65.gif (32)

์™€ ๊ฐ™๋‹ค. ์ž„์˜์  PICCD76.gif์—์„œ์˜ ์ˆ˜ํ‰์œ ์†์„ PICCD96.gif๋ผ๊ณ  ์ •์˜ํ•˜๊ณ  PICCDC6.gif๋ฅผ PICCDE6.gif์— ๋Œ€ํ•˜์—ฌ Taylor ์ „๊ฐœํ•˜๋ฉด

PICCEE1.gif

(33)

์™€ ๊ฐ™์œผ๋ฉฐ, PICCEE2.gif์—์„œ PICCEF3.gif๊นŒ์ง€ ์ ๋ถ„ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICD08A.gif

(34)

Eq. (34)๋ฅผ Eq. (32)์— ๋Œ€์ž…ํ•˜๋ฉด,

      

PICD231.gif

(35)

์ด๋ฉฐ ์ด๋ฅผ ๋‹ค์‹œ PICD232.gif์— ๋Œ€ํ•ด์„œ ๋ฏธ๋ถ„ํ•˜๋ฉด, 

PICD2A0.gif (36)

์™€ ๊ฐ™๋‹ค. Eqs. (35)์™€ (36)์„ Eq. (33)์— ๋Œ€์ž…ํ•˜๋ฉด,

PICD39B.gif

(37)

์ด๋ฉฐ, Eq. (37)์„ Eq. (31)์— ๋Œ€์ž…ํ•˜๋ฉด

PICD3BC.gif (38)

PICD4E6.gif

์„ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

Eqs. (37) and (38)์„ ์—ฐ์ง๋ชจ๋ฉ˜ํ…€์‹ (26)์— ๋Œ€์ž…ํ•˜์—ฌ PICD506.gif๋ฅผ ๊ตฌํ•œ ๋‹ค์Œ, ๋™์—ญํ•™์  ์ž์œ ์ˆ˜๋ฉด ๊ฒฝ๊ณ„์กฐ๊ฑด์ธ Eq. (29)๋ฅผ ์ด์šฉํ•˜์—ฌ PICD516.gif์—์„œ ์ž์œ ์ˆ˜๋ฉด PICD527.gif๊นŒ์ง€ ์ ๋ถ„ํ•˜๋ฉด ์••๋ ฅ์˜ ์—ฐ์ง๋ถ„ํฌ๋ฅผ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๊ตฌํ•  ์ˆ˜ ์žˆ๋‹ค.

PICD632.gif 

(39)

Eqs. (37)~(39)๋ฅผ ์ˆ˜ํ‰๋ชจ๋ฉ˜ํ…€์‹ (25)์— ๋Œ€์ž…ํ•˜๋ฉด ์ž๋ฆฟ์ˆ˜๊ฐ€ PICD662.gif์˜ ํฌ๊ธฐ์ธ ๋‹ค์Œ๊ณผ ๊ฐ™์€ ์ฒซ ๋ฒˆ์งธ Boussinesq ๋ฐฉ์ •์‹์ธ ์šด๋™๋ฐฉ์ •์‹์„ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

PICD6E0.gif

PICD76D.gif (40)

์—ฐ์†๋ฐฉ์ •์‹ (24)๋ฅผ ์—ฐ์ง์ ๋ถ„ํ•˜๊ณ  ์šด๋™ํ•™์  ์ˆ˜๋ฉด๊ฒฝ๊ณ„์กฐ๊ฑด (28)์„ ์ ์šฉํ•˜๋ฉด

PICD7EB.gif (41)

๋ฅผ ์–ป์„ ์ˆ˜ ์žˆ์œผ๋ฉฐ ์—ฌ๊ธฐ์— Eq. (37)์„ ๋Œ€์ž…ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๋‘ ๋ฒˆ์งธ Boussinesq ๋ฐฉ์ •์‹์ธ ์—ฐ์†๋ฐฉ์ •์‹์„ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

PICD963.gif (42)

       

Eqs. (42) and (40)์„ ์œ ์ฐจ์›์œผ๋กœ ํ™˜์›ํ•˜๊ณ  PICD974.gif๋กœ ์ •์˜ํ•˜๋ฉด (PICD994.gif), ๊ณต๊ทน๋งค์ฒด์—์„œ์˜ 2D Boussinesq ๋ฐฉ์ •์‹์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICDA7F.gif

(43)

PICDB5B.gif  

PICDBAA.gif (44)

์—ฌ๊ธฐ์„œ, PICDBDA.gif, PICDC0A.gif, PICDC2A.gif, PICDC2B.gif์ด๋‹ค. ์ƒ๊ธฐ ์‹๋“ค์„ Darcy ์œ ์† PICDC3C.gif์œผ๋กœ ํ‘œํ˜„ํ•˜๊ณ  Eq. (44)์— Eq. (11)์˜ ๋‚ด๋ถ€๋งˆ์ฐฐํ•ญ์„ ๋ถ€๊ฐ€ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICDCE9.gif

PICDD67.gif (45)

PICDE91.gif   (46)

Eqs. (45) and (46)์€ ๊ณต๊ทน๋ฅ ์ด PICDEA1.gif์ด๋ฉด ์ˆœ์ˆ˜ ์œ ์ฒดํ๋ฆ„์— ๋Œ€ํ•œ Walkley (1999)์™€ ๊ฒฐ๊ณผ์™€ ์ •ํ™•ํžˆ ์ผ์น˜ํ•œ๋‹ค(๊ธฐ์กด์˜ Dingemans (1997, p.537)์˜ ๊ฒฐ๊ณผ์™€๋„ ์ผ์น˜ํ•˜๋‚˜ Nwogu (1993)์˜ ๊ฒฐ๊ณผ์™€๋Š” Eq. (46)์˜ 4, 5๋ฒˆ์งธ ํ•ญ์—์„œ ์•ฝ๊ฐ„์˜ ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ•จ). ํ•œํŽธ, Nwogu๋Š” ์ ์ • PICDEB2.gif๊ฐ’์œผ๋กœ์„œ PICDEC3.gif์„ ์ œ์•ˆํ•˜์˜€๋‹ค.

Eqs. (45) and (46)์„ ์‚ผ์ฐจ์›์œผ๋กœ ํ™•์žฅํ•˜๋ฉด,

PICDF12.gif

PICDFBF.gif (47)

PICE0AA.gif 

PICE0F9.gifPICE167.gif

PICE1B7.gif (48)

์™€ ๊ฐ™๋‹ค. ์—ฌ๊ธฐ์„œ, PICE1E6.gif๋Š” PICE207.gif์—์„œ์˜ ์ˆ˜ํ‰์œ ์† ์„ฑ๋ถ„์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. Wei et al. (1995)๋Š” ์ž”๋ฅ˜ํ•ญ์ด PICE237.gif์ธ Eqs. (47) and (48)์˜ ๋น„์„ ํ˜•์„ฑ์„ ๋ณด๋‹ค ํ™•์žฅํ•˜์—ฌ ์ž”๋ฅ˜ํ•ญ์„ ์ฒœ์ˆ˜ํŒŒ๋ผ๋ฏธํ„ฐ PICE238.gif๊ฐ€ ์ฃผ๋„ํ•˜๋Š” PICE258.gif์˜ ์—ฐ์†๋ฐฉ์ •์‹๊ณผ ์šด๋™๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜์˜€๋‹ค.

Boussinesq ๋ฐฉ์ •์‹์— ๋Œ€ํ•œ ์ˆ˜์น˜ํ•ด์„์€ Wei et al. (1995, 1999), Nwogu and Demirbilek (2001)์— ์ œ์‹œ๋˜์–ด ์žˆ๋‹ค. ์ˆ˜์น˜ํ•ด์„์˜ ์•ˆ์ •์„ฑ์„ ์œ„ํ•˜์—ฌ ์‹œ๊ฐ„ ๋ฐ ๊ณต๊ฐ„์ฐจ๋ถ„์˜ ์ฆ๋ถ„์„ ์ผ๋ฐ˜์ ์ธ Courant ์กฐ๊ฑด์— ๋”ฐ๋ผ ๊ฒฐ์ •ํ•˜๋ฉด ๋˜๋‚˜ ๋ณธ ํ™•์žฅํ˜• ๋ฐฉ์ •์‹์—์„œ ๋ชจ๋“  ๊ฒฉ์ž์—์„œ์˜ ์ˆ˜์‹ฌ์กฐ๊ฑด์„ ๋ถ„์‚ฐ์„ฑ์˜ ์‹ฌํ•ด์ธก ์œ ํšจํ•œ๊ณ„์ธ ์ˆ˜์‹ฌ/ํŒŒ์žฅ=0.5 ์ด๋‚ด๋กœ ์œ ์ง€ํ•˜๋Š” ๊ฒƒ ๊ทธ๋ฆฌ๊ณ  ํ•œ ํŒŒ์žฅ๋‚ด์— ์ตœ์†Œ 8๊ฐœ ์ด์ƒ์˜ ๊ฒฉ์ž๋ฅผ ๋‘๋Š” ๊ฒƒ ๋“ฑ์— ์œ ์˜ํ•˜์—ฌ์•ผ ํ•œ๋‹ค. ํŠนํžˆ, ๋ถˆ๊ทœ์น™ํŒŒ ์ž…์‚ฌ์กฐ๊ฑด์„ ์ฑ„ํƒํ•˜๋Š” ๊ฒฝ์šฐ๋Š” ๊ณ ์ฃผํŒŒ์ˆ˜ ์„ฑ๋ถ„์—์„œ์˜ ํ•ด์ƒ๋„ ๋ฐ ์ˆ˜์น˜ํ•ด์„์˜ ์•ˆ์ •์„ฑ์„ ์œ„ํ•˜์—ฌ ์‹œ๊ฐ„ ๋ฐ ๊ณต๊ฐ„์ฆ๋ถ„, ์ „์ฒด ๊ณ„์‚ฐ์‹œ๊ฐ„ ๋“ฑ์„ ์„ธ์‹ฌํžˆ ๊ณ ๋ คํ•  ํ•„์š”๊ฐ€ ์žˆ๋‹ค.

3.2 ์ง๋ฆฝ์‹ ๊ณต๊ทน ๋ฐฉํŒŒ์ œ์— ๋Œ€ํ•œ ์ ์šฉ

์œ ๋„๋œ ๊ณต๊ทน๋งค์ฒด Boussinesq ๋ฐฉ์ •์‹์˜ ์ ์šฉ์„ฑ์„ ๊ฒ€ํ† ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ง๋ฆฝ์‹ ๊ณต๊ทน ๋ฐฉํŒŒ์ œ์˜ ๋ฐ˜์‚ฌ์œจ๊ณผ ํˆฌ๊ณผ์œจ์„ ๊ฐ๊ฐ ๊ณ„์‚ฐํ•˜์—ฌ ๊ธฐ์กด์˜ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•˜์˜€๋‹ค. ์ˆ˜์น˜ํ•ด์„์€ Eqs. (45) and (46)์— Wei et al. (1995)์˜ Predictor-Corrector ๋ฐฉ๋ฒ•์„ ์ ์šฉํ•˜์˜€์œผ๋ฉฐ ๊ธฐ์กด์˜ Boussinesq ๋ฐฉ์ •์‹ ๋ชจ๋ธ(Chun et al., 2006; Chun, 2007)์„ ์ˆ˜์ •ํ•˜์—ฌ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๊ณ„์‚ฐ์— ์‚ฌ์šฉ๋œ ์ˆ˜์น˜์ˆ˜์กฐ๋Š” Fig. 3์—์„œ ๋ณด์ด๋Š” ๋ฐ”์™€ ๊ฐ™์ด ์ˆ˜์กฐ์˜ ์ขŒยท์šฐ๋‹จ์— ํŒŒ๋ฅผ ํก์ˆ˜ํ•˜๊ธฐ ์œ„ํ•œ ์ŠคํŽ€์ง€์ธต์„ ์„ค์น˜ํ•˜์˜€์œผ๋ฉฐ ๋ฐ˜์‚ฌ์œจ๊ณผ ํˆฌ๊ณผ์œจ์„ ๊ธฐ๋กํ•˜๊ธฐ ์œ„ํ•œ ์ˆ˜์น˜ํŒŒ๊ณ ๊ณ„๋“ค์„ ๊ณต๊ทน๋ฐฉํŒŒ์ œ ์ „ยทํ›„์— ์„ค์น˜ํ•˜์˜€๋‹ค. ์•„์šธ๋Ÿฌ, ํ•ด์„๊ฒฐ๊ณผ์˜ ์ ์ ˆํ•œ ํ‰๊ฐ€๋ฅผ ์œ„ํ•˜์—ฌ ๊ธฐ์กด์— ์ˆ˜๋ฆฝ๋œ ๊ฒฝ๊ณ„์š”์†Œ๋ฒ• ๋ชจ๋ธ(Chun et al., 2007)๋„ ํ•จ๊ป˜ ์ ์šฉํ•˜์˜€๋‹ค. ๋ณธ ๊ฒฝ๊ณ„์š”์†Œ๋ฒ•์—์„œ๋Š” Eq. (11)์—์„œ ์ด๋ฅ˜ํ•ญ์„ ๋ฌด์‹œํ•˜๊ณ  ๊ฐ€์ƒ์งˆ๋Ÿ‰๊ณ„์ˆ˜๋ฅผ PICE268.gif=0์œผ๋กœ ํ•˜์—ฌ ์ ์šฉํ•œ ๊ฒƒ์ด๋‹ค.

KSCE_35_5_05_F3.jpg

Fig. 3. Scheme of the Numerical Wave Flume

Table 2. Experimental Conditions

Specification

Source

DepthPIC8A24.gif (m)

Wave periodPIC8A35.gif (sec)

Wave

steepness PIC8AA3.gif

Rubble diameterPIC8AC4.gif (m)

Porosity

PIC8AD4.gif

Structural widthPIC8AD5.gif (m)

Sollitt and Cross (1976)

0.549

1.70

0.003-0.015

0.0348

0.437

0.549

Keulegan (1973)

0.300

1.94

0.002-0.020

0.0253

0.460

0.158, 0.317

์ˆ˜์น˜ํ•ด์„์˜ ์ž…๋ ฅ์กฐ๊ฑด์€ Table 2์—์„œ ๋ณด์ด๋Š” ๋ฐ”์™€ ๊ฐ™์ด Sollitt and Cross (1976)์™€ Keulegan (1973)์˜ ์ˆ˜๋ฆฌ์‹คํ—˜๋“ค๊ณผ ๋™์ผํ•˜๊ฒŒ ์ทจํ•˜์˜€์œผ๋ฉฐ ๊ณ„์‚ฐ๊ฒฐ๊ณผ๋ฅผ ์ด๋“ค์˜ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ๋“ค๊ณผ ๋น„๊ตํ•˜์˜€๋‹ค. ๋ณธ ์ˆ˜๋ฆฌ์‹คํ—˜๋“ค์€ ๊ณ ์ •๋œ ์ฃผ๊ธฐ์— ํŒŒ๊ณ ๋ฅผ ์ฆ๊ฐ€์‹œ์ผœ๊ฐ€๋ฉฐ ํŒŒ๊ณ ๊ณ„๋ฅผ ์ด์šฉํ•˜์—ฌ ๋ฐ˜์‚ฌ์œจ๊ณผ ํˆฌ๊ณผ์œจ์„ ์ธก์ •ํ•˜์˜€๋‹ค. ์‹ค์ œ ๋ณธ ์ˆ˜๋ฆฌ์‹คํ—˜๋“ค์€ ์ฃผ๊ธฐ์™€ ํŒŒ๊ณ ๋ฅผ ๋‹ฌ๋ฆฌํ•˜๋Š” ๋‹ค์–‘ํ•œ ์กฐ๊ฑด์—์„œ ์ˆ˜ํ–‰๋˜์—ˆ์œผ๋‚˜ ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ํ˜„ ์ˆ˜์น˜ํ•ด์„๊ธฐ๋ฒ•์˜ ์„ฑ๋Šฅ์„ ์ผ์ฐจ์ ์œผ๋กœ ๊ฒ€ํ† ํ•  ๋ชฉ์ ์œผ๋กœ Table 2์™€ ๊ฐ™์ด ๊ฐ๊ฐ ํ•œ ์ฃผ๊ธฐ๋“ค๋งŒ์„ ์„ ๋ณ„ํ•˜์—ฌ ์ˆ˜์น˜ํ•ด์„์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

์ˆ˜์น˜ํ•ด์„์—์„œ ๋ฐ˜์‚ฌ์œจ์€ Park et al. (1992)์˜ ์‚ผ์ ๋ฒ•์„ ์ ์šฉํ•˜์—ฌ ๊ณ„์‚ฐํ•˜์˜€์œผ๋ฉฐ ํˆฌ๊ณผ์œจ์€ zero-up-crossing ๊ธฐ๋ฒ•์„ ์ ์šฉํ•˜์—ฌ ๊ณ„์‚ฐํ•˜์˜€๋‹ค. ํŒŒ๊ณ ๊ณ„ ๊ณ„์ธก์‹œ๊ฐ„์€ ์กฐํŒŒ๊ธฐ - ์ˆ˜์กฐ์šฐ๋‹จ์˜ ๊ฑฐ๋ฆฌ๋ฅผ ๊ตฐ์†๋„๋กœ 3 ์™•๋ณตํ•œ ์ดํ›„๋ถ€ํ„ฐ 6 ์™•๋ณตํ•  ๋•Œ๊นŒ์ง€๋กœ ํ•˜์˜€๋‹ค. ๊ณ„์‚ฐ์กฐ๊ฑด์œผ๋กœ์„œ๋Š” PICE279.gif = PICE28A.gif์œผ๋กœ ํ•˜์˜€์œผ๋ฉฐ ์‹œ๊ฐ„์ฆ๋ถ„์€ Courant ์กฐ๊ฑด์„ ์ ์šฉํ•˜์—ฌ PICE2C9.gif์™€ ๊ฐ™์ด ์ทจํ•˜์˜€๋‹ค. ์—ฌ๊ธฐ์„œ, PICE2DA.gif๋Š” ์„ ํ˜•ํŒŒ ํŒŒ์†์„ ์˜๋ฏธํ•œ๋‹ค. Eq. (15)์™€ Eq. (16)์—์„œ์˜ ๋‚ด๋ถ€๋งˆ์ฐฐ๊ณ„์ˆ˜๋Š” ๊ฐ๊ฐ PICE2EA.gif = 1150 PICE2EB.gif, PICE31B.gif = 2.7 PICE31C.gif๋กœ ์ทจํ•˜์˜€๋‹ค.

๋ณธ ์ˆ˜์น˜ํ•ด์„์—์„œ๋Š” Eq. (10)์—์„œ์˜ PICE33D.gif์˜ ๊ฐ’์— ๋Œ€ํ•œ ์ˆ˜์น˜์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค. ์ฆ‰, ์‡„์„์— ๋Œ€ํ•œ ๋ถ€๊ฐ€์งˆ๋Ÿ‰๊ณ„์ˆ˜ PICE3CA.gif๋ฅผ ๋™์ผ ์ง๊ฒฝ์„ ๊ฐ–๋Š” ๊ตฌ์ฒด์˜ ์ด๋ก ์  ๊ฐ’ PICE3DB.gif์—์„œ ๊ด€์„ฑ๋ ฅ์„ ๋ฌด์‹œํ–ˆ์„ ๋•Œ์˜ PICE3FB.gif, ๊ทธ๋ฆฌ๊ณ  PICE40C.gif์— ์ด๋ฅด๊ธฐ ๊นŒ์ง€ ๋‹ค์–‘ํ•œ ๊ฐ’์„ ์‹œ๋„ํ•˜์—ฌ ๊ณ„์‚ฐ๊ฒฐ๊ณผ๋ฅผ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•˜์˜€๋‹ค. Figs. 4 and 5๋Š” Sollitt and Cross (1976)์— ๋Œ€ํ•œ ๊ณ„์‚ฐ๊ฒฐ๊ณผ๋ฅผ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ•œ ๊ฒƒ์ด๋‹ค. ๋ฐ˜์‚ฌ์œจ๊ณผ ํˆฌ๊ณผ์œจ ๊ณตํžˆ PICE42C.gif์ผ ๋•Œ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๊ฐ€์žฅ ์ž˜ ์ผ์น˜ํ•จ์„ ๋ณผ ์ˆ˜ ์žˆ๋‹ค. ์ด๋Š” PICE44C.gif์—์„œ ๋ถ€๊ฐ€์งˆ๋Ÿ‰๊ณ„์ˆ˜๊ฐ€ PICE45D.gif์ด ๋จ์„ ์˜๋ฏธํ•œ๋‹ค. ์ด์™€ ๊ฐ™์ด ์Œ์˜ ๊ฐ’์„ ๊ฐ–๋Š” ๋ถ€๊ฐ€์งˆ๋Ÿ‰๊ณ„์ˆ˜๊ฐ€ ๋ฌผ๋ฆฌ์ ์œผ๋กœ ์ „ํ˜€ ๋ถˆ๊ฐ€๋Šฅํ•œ ๊ฒƒ์€ ์•„๋‹ˆ๋‚˜ ๋ณธ ๋ฌธ์ œ์—์„œ์™€ ๊ฐ™์€ ๊ทน๋‹จ์ ์ธ ๊ฐ’ PICE46D.gif์ด ๋ฌผ๋ฆฌ์ ์ธ ํƒ€๋‹น์„ฑ์„ ๊ฐ–๋Š”๋‹ค๊ณ  ๋ณด๊ธฐ๋Š” ๋งค์šฐ ์–ด๋ ค์šธ ๊ฒƒ์œผ๋กœ ๋ณด์ธ๋‹ค. ๋Œ€์‹  ๊ณต๊ทน๋งค์ฒด ํ๋ฆ„์—์„œ ์‡„์„๋ถ€๋ถ„์— ์˜ํ•œ ๊ด€์„ฑ์ €ํ•ญ์€ ํ˜•์„ฑ๋˜์ง€ ์•Š์œผ๋ฉฐ ํ˜•์„ฑ๋œ๋‹ค ํ•˜๋”๋ผ๋„ ๊ฑฐ์˜ ๋ฌด์‹œ๋  ์ˆ˜ ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ๊ฐ„์ฃผํ•˜๋Š” ๊ฒƒ์ด ํƒ€๋‹นํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ํ•œํŽธ, ๊ฒฝ๊ณ„์š”์†Œ๋ฒ•์˜ ๊ฒฐ๊ณผ๋Š” ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ต์  ์ž˜ ์ผ์น˜ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚˜ ์žˆ๋‹ค. ๋ณธ ๊ฒฝ๊ณ„์š”์†Œ๋ฒ•์˜ ๊ฒฐ๊ณผ๋„ PICE47E.gif์˜ ์กฐ๊ฑดํ•˜์—์„œ ๊ณ„์‚ฐ๋œ ๊ฒƒ์ด๋‹ค(Sollitt and Cross (1972)๋„ PICE4AE.gif์„ ํŠน์ •ํ•˜๊ธฐ๊ฐ€ ์–ด๋ ค์šด ์ ์„ ๊ณ ๋ คํ•˜์—ฌ PICE4BF.gif๋กœ ํ•˜์—ฌ ์ˆ˜์น˜ํ•ด์„์„ ์ˆ˜ํ–‰ํ•œ ๋ฐ” ์žˆ๋‹ค). ๋˜ํ•œ, Fig. 4์˜ ๋ฐ˜์‚ฌ์œจ์—์„œ PICE4C0.gif์— ๋Œ€ํ•œ Boussinesq ๋ชจ๋ธ์˜ ๊ฒฐ๊ณผ์™€ ๊ฒฝ๊ณ„์š”์†Œ๋ฒ• ๊ฒฐ๊ณผ๊ฐ€ ์ „ PICE4FF.gif์˜ ๋ฒ”์œ„์—์„œ ๊ฑฐ์˜ ์ผ์ •ํ•œ ์ฐจ์ด๋ฅผ ๋ณด์ด๊ณ  ์žˆ์œผ๋ฉฐ ๋ณ€ํ™” ์„ฑํ–ฅ์ด ๊ฑฐ์˜ ๋™์ผํ•จ์„ ๋ณผ ์ˆ˜ ์žˆ๋‹ค. ์ด๋Š” ๊ฒฝ๊ณ„์š”์†Œ๋ฒ•์—์„œ ์ด๋ฅ˜ํ•ญ์ด ์ œ์™ธ๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์ธ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

KSCE_35_5_05_F4.jpg

Fig. 4. Comparison of Calculated Reflection Coefficients and Sollitt and Cross's Experimental Results

KSCE_35_5_05_F5.jpg

Fig. 5. Comparison of Calculated Transmission Coefficients and Sollitt and Cross's Experimental Results

Fig. 6์€ PICE510.gif์˜ ์กฐ๊ฑด์—์„œ ํŒŒ๋ž‘์˜ 1 ์ฃผ๊ธฐ ๋‚ด์—์„œ ๋„ค ๊ฐœ์˜ ๋™์ผ ์‹œ๊ฐ„๊ฐ„๊ฒฉ๋งˆ๋‹ค ๊ณ„์ธกํ•œ ์ „ ์ˆ˜์กฐ์—ฐ์žฅ(150 m)์—์„œ์˜ ์Šค๋ƒ… ํŒŒํ˜•์ด๋‹ค. ๊ณต๊ทน๋ฐฉํŒŒ์ œ ์ „๋ฉด์—๋Š” ๋ถ€๋ถ„ ์ค‘๋ณตํŒŒ์˜ ํ˜•์„ฑ์— ๋”ฐ๋ฅธ ํŒŒํ˜•์˜ ์‹œ๊ฐ„์  ๋ณ€ํ™”๋ฅผ ๋ณผ ์ˆ˜ ์žˆ์œผ๋‚˜ ํ›„๋ฉด์—๋Š” ์ผ์ • ์ง„ํญ์˜ ํˆฌ๊ณผํŒŒ๊ฐ€ ํ˜•์„ฑ๋˜์–ด ์žˆ์Œ์„ ๋ณผ ์ˆ˜ ์žˆ๋‹ค.

KSCE_35_5_05_F6.jpg

Fig. 6. Wave Profiles at 4 Equal Time Intervals Within a Wave Period (PICE520.gif = 0.549m, PICE531.gif = 1.7 s, PICE542.gif = 0.05 m, PICE552.gif = 0.79, PICE572.gif = 0.30)

Keulegan์˜ ์ˆ˜๋ฆฌ์‹คํ—˜ ์กฐ๊ฑด์— ๋Œ€ํ•œ ๊ณ„์‚ฐ๊ฒฐ๊ณผ๋ฅผ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€ ํ•จ๊ป˜ Figs. 7~10์— ๋„์‹œํ•˜์˜€๋‹ค. ์ƒ๊ธฐ Sollitt์˜ ์‹คํ—˜์กฐ๊ฑด์— ๋Œ€ํ•œ ๊ฒฐ๊ณผ์—์„œ์™€ ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ PICE583.gif์˜ ์กฐ๊ฑด์—์„œ ์ผ์น˜์ •๋„๊ฐ€ ๊ฐ€์žฅ ์–‘ํ˜ธํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ์ „๋ฐ˜์ ์œผ๋กœ ํˆฌ๊ณผ์œจ์—์„œ๋Š” ๊ณ„์‚ฐ์น˜์™€ ์‹คํ—˜์น˜๊ฐ€ ๋น„๊ต์  ์ž˜ ์ผ์น˜ํ•˜๋Š” ๋ฐ˜๋ฉด ๋ฐ˜์‚ฌ์œจ์—์„œ๋Š” ์ƒ๋‹น ์ •๋„์˜ ํŽธ์ฐจ๊ฐ€ ์กด์žฌํ•จ์„ ๋ณผ ์ˆ˜ ์žˆ๋‹ค. ๋ฐ˜์‚ฌ์œจ์—์„œ ๋Œ€์ฒด์ ์œผ๋กœ Boussinesq ๋ชจ๋ธ๊ฒฐ๊ณผ์™€ ๊ฒฝ๊ณ„์š”์†Œ๋ฒ•์˜ ๊ฒฐ๊ณผ๊ฐ€ ์œ ์‚ฌํ•œ ๊ฒƒ์œผ๋กœ ๋ฏธ๋ฃจ์–ด๋ณด์•„ ๋ณธ ๊ณ„์‚ฐ์น˜์™€ ์‹คํ—˜์น˜์™€์˜ ์ฐจ์ด๋Š” ๋ฐ˜์‚ฌ์œจ์˜ ์ธก์ •๋ฐฉ๋ฒ•์˜ ์ฐจ์ด์— ์˜ํ•˜์—ฌ ๋ฐœ์ƒํ•œ ๊ฒƒ์ด๊ฑฐ๋‚˜ ์•„๋‹ˆ๋ฉด ๊ณต๊ทน๋งค์ฒด์—์„œ์˜ ํ† ๋ฆฝ์ž์— ์˜ํ•œ ๋‚ด๋ถ€๋งˆ์ฐฐ๋ ฅ์˜ ์ฐจ์ด์— ๊ธฐ์ธํ•œ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

KSCE_35_5_05_F7.jpg

Fig. 7. Comparison of Calculated Reflection Coefficients and Keulegan's Experimental Results (PICE584.gif = 0.15 m)

KSCE_35_5_05_F8.jpg

Fig. 8. Comparison of Calculated Transmission Coefficients and Keulegan's Experimental Results (PICE5C5.gif = 0.15 m)

KSCE_35_5_05_F9.jpg

Fig. 9. Comparison of Calculated Reflection Coefficients and Keulegan's Experimental Results (PICE595.gif = 0.30 m)

KSCE_35_5_05_F10.jpg

Fig. 10. Comparison of Calculated Transmission Coefficients and Keulegan's Experimental Results (PICE5C6.gif = 0.30 m)

Keulegan์˜ ์ˆ˜๋ฆฌ์‹คํ—˜์—์„œ๋Š” 1๊ฐœ์˜ ํŒŒ๊ณ ๊ณ„๋ฅผ ์ด๋™์‹œ์ผœ๊ฐ€๋ฉฐ ์–ป์€ ์‹œ๊ทธ๋„๋กœ ๋ฐ˜์‚ฌ์œจ์„ ๊ตฌํ•˜์˜€์ง€๋งŒ ๋ณธ Boussinesq ์ˆ˜์น˜ํ•ด์„์—์„œ๋Š” 3๊ฐœ์˜ ๋…๋ฆฝ๋œ ํŒŒ๊ณ ๊ณ„์˜ ์‹œ๊ทธ๋„๋ฅผ ์ด์šฉํ•˜๋Š” ์‚ผ์ ๋ฒ•์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๋‚ด๋ถ€๋งˆ์ฐฐ๋ ฅ์— ๋Œ€ํ•ด์„œ๋Š” Eq. (11)์—์„œ ์•Œ ์ˆ˜ ์žˆ๋“ฏ์ด ์ˆ˜๋ฆฝ์ž์˜ ์†๋„์— ์˜์กดํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์ˆ˜์น˜ํ•ด์„์˜ ์ •ํ™•๋„๋Š” ์ˆ˜๋ฆฝ์ž ๊ถค๋„์œ ์†(orbital velocity)์˜ ์—ฐ์ง๋ถ„ํฌ๋ฅผ ์–ผ๋งˆ๋‚˜ ์ž˜ ์žฌํ˜„ํ•˜๋Š”๊ฐ€์— ๋‹ฌ๋ ค์žˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜, ๋ณธ ์ˆ˜์น˜ํ•ด์„์—์„œ ์‚ฌ์šฉํ•œ ํ™•์žฅํ˜• Boussinesq ๋ชจ๋ธ์€ ์ฃผ๋กœ ์‹ฌํ•ด์—ญ์—์„œ์˜ ๋ถ„์‚ฐ์„ฑ์˜ ์žฌํ˜„ ์ •๋„๋ฅผ ๊ฐœ์„ ํ•˜๊ธฐ ์œ„ํ•œ ๊ฒƒ์œผ๋กœ์„œ ์ˆ˜๋ฆฝ์ž์˜ ๊ถค๋„์œ ์†์„ ์ž˜ ์žฌํ˜„ํ•œ๋‹ค๊ณ  ๋ณด๊ธฐ๋Š” ์–ด๋ ต๋‹ค. ์ผ๋‹จ, Eqs. (37) and (38)์—์„œ ์ˆ˜๋ฆฝ์ž ์œ ์†์˜ ์˜ค์ฐจํฌ๊ธฐ๋ฅผ PICE5F5.gif๋กœ ์ž‘๊ฒŒ ์ œ์‹œํ•˜๊ณ ๋Š” ์žˆ์œผ๋‚˜ ๋ถ„์‚ฐ์„ฑ๊ณผ ๋น„์„ ํ˜•์„ฑ์„ ๋‹ฌ๋ฆฌํ•˜๋Š” ์—ฌ๋Ÿฌ ํŒŒ๋ž‘์กฐ๊ฑด๋“ค์— ๋Œ€ํ•œ ๋ณ„๋„์˜ ์ ๊ทน์ ์ธ ๊ฒ€์ฆ์ด ํ•„์š”ํ•  ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ํ•œํŽธ, ์ˆ˜์‹ฌ์„ ์—ฌ๋Ÿฌ ์ธต์œผ๋กœ ๋‚˜๋ˆ„์–ด ์ˆ˜๋ฆฝ์ž ๊ถค๋„์œ ์† ๊ณ„์‚ฐ์˜ ํ•ด์ƒ๋„๋ฅผ ๋†’์ด๊ธฐ ์œ„ํ•œ ๊ธฐ๋ฒ•๋“ค์ด ์ตœ๊ทผ ์—ฐ๊ตฌ๋œ ๋ฐ” ์žˆ๋‹ค(Lynett and Liu, 2004; Hsiao et al., 2005). ์ด๋“ค ๊ธฐ๋ฒ•๋“ค์„ ๋ณธ ์ˆ˜์น˜ํ•ด์„์— ์‚ฌ์šฉํ•จ์œผ๋กœ์จ ๊ณ„์‚ฐ์˜ ์ •ํ™•๋„๋ฅผ ์ œ๊ณ ํ•  ์ˆ˜ ์žˆ์„ ๊ฒƒ์ด๋‹ค. ์•„์šธ๋Ÿฌ, ์ˆ˜๋ฆฌ์‹คํ—˜ ์—ญ์‹œ ๋งค์šฐ ์˜ค๋ž˜์ „์— ์ˆ˜ํ–‰๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์— ์ตœ์†Œํ•œ ๋ช‡ ๊ฐœ ์กฐ๊ฑด์— ๋Œ€ํ•ด์„œ๋Š” ๋ฐ˜์‚ฌ์œจ ๋ฐ ํˆฌ๊ณผ์œจ์˜ ํ™•์ธ์‹คํ—˜์ด ์ˆ˜ํ–‰๋  ํ•„์š”๊ฐ€ ์žˆ์„ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค.

4. ๊ฒฐ ๋ก 

๊ณต๊ทน๋งค์ฒด ํ๋ฆ„์— ๋Œ€ํ•œ Reynolds ์ด์†ก์ •๋ฆฌ๋ฅผ ์ ์šฉํ•˜์—ฌ ๊ณต๊ทน๋งค์ฒด์—์„œ์˜ Navier-Stokes ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜์˜€์œผ๋ฉฐ ์ด๋ฅผ ๊ธฐ์กด์˜ ์œ ์‚ฌ์—ฐ๊ตฌ ๊ฒฐ๊ณผ๋“ค๊ณผ ๋น„๊ตํ•˜์˜€๋‹ค. ๋˜ํ•œ, ์œ ๋„๋œ N-S ๋ฐฉ์ •์‹์„ ์ด์šฉํ•˜์—ฌ ๊ณต๊ทน๋งค์ฒด ๋‚ด์™ธ์—์„œ ํŒŒ๋™์žฅ์˜ ๋น„์„ ํ˜•์„ฑ๊ณผ ๋ถ„์‚ฐ์„ฑ์„ ์ ์ ˆํžˆ ์žฌํ˜„ํ•˜๊ธฐ ์œ„ํ•œ ํ™•์žฅํ˜• Boussinesq ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜์˜€๋‹ค. ๊ทธ๋ฆฌ๊ณ  ์ด๋“ค ๋ฐฉ์ •์‹์˜ ์œ ํšจ์„ฑ์„ ๊ฒ€์ฆํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ณต๊ทน๋ฐฉํŒŒ์ œ์˜ ๋ฐ˜์‚ฌ์œจ ๋ฐ ํˆฌ๊ณผ์œจ์— ๋Œ€ํ•œ ์ˆ˜์น˜ํ•ด์„์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ๊ทธ ๊ฒฐ๊ณผ๋ฅผ ๊ธฐ์กด ์ˆ˜๋ฆฌ ์‹คํ—˜๋“ค๊ณผ์˜ ๋น„๊ตํ•˜์˜€๋‹ค. ์„ธ๋ถ€์ ์ธ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

(1)์ˆ˜์น˜์‹คํ—˜์„ ์ˆ˜ํ–‰ํ•œ ๊ฒฐ๊ณผ, ๊ณต๊ทน๋ฐฉํŒŒ์ œ์˜ ๋ฐ˜์‚ฌ์œจ๊ณผ ํˆฌ๊ณผ์œจ์€ ํ† ๋ฆฝ์ž์˜ ๊ฐ€์ƒ์งˆ๋Ÿ‰๊ณ„์ˆ˜์— ๋ฏผ๊ฐํ•˜๊ฒŒ ๋ฐ˜์‘ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ์œผ๋ฉฐ, ๊ฐ€์ƒ์งˆ๋Ÿ‰๊ณ„์ˆ˜๋ฅผ ์˜์œผ๋กœ ์ฒ˜๋ฆฌํ–ˆ์„ ๊ฒฝ์šฐ์— ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€์˜ ์ผ์น˜์ •๋„๊ฐ€ ๊ฐ€์žฅ ์–‘ํ˜ธํ•œ ๊ฒƒ์œผ๋กœ ๋‚˜ํƒ€๋‚ฌ๋‹ค. ์ด๋Š” ๊ณต๊ทน๋งค์ฒด ํŒŒ๋™์žฅ์—์„œ ํ† ๋ฆฝ์ž์— ์˜ํ•œ ์ €ํ•ญ์€ ์ฃผ๋กœ ๋‚ด๋ถ€๋งˆ์ฐฐ๋กœ ๋‚˜ํƒ€๋‚˜๋ฉฐ ๊ด€์„ฑ์ €ํ•ญ์€ ๋งค์šฐ ๋ฏธ๋ฏธํ•˜๊ฒŒ ํ˜•์„ฑ๋จ์„ ์˜๋ฏธํ•œ๋‹ค.

(2)์ˆ˜์น˜ํ•ด์„๊ฒฐ๊ณผ์—์„œ ํˆฌ๊ณผ์œจ์€ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€์˜ ์–‘ํ˜ธํ•œ ์ผ์น˜๋ฅผ ๋ณด์ด๋Š” ๋ฐ˜๋ฉด ๋ฐ˜์‚ฌ์œจ์—์„œ๋Š” ๋‹ค์†Œ ์ฐจ์ด๊ฐ€ ๋ฐœ์ƒํ•˜์˜€๋‹ค. Boussnesq ๋ฐฉ์ •์‹ ๋ชจ๋ธ์˜ ๊ฒฐ๊ณผ๊ฐ€ ๊ฒฝ๊ณ„์š”์†Œ๋ฒ•์˜ ์ ์šฉ๊ฒฐ๊ณผ์™€ ์ „๋ฐ˜์ ์œผ๋กœ ์œ ์‚ฌํ•˜๊ฒŒ ๋‚˜ํƒ€๋‚œ ๊ฒƒ์œผ๋กœ ๋ณด์•„ ์ˆ˜๋ฆฌ์‹คํ—˜๊ฒฐ๊ณผ์™€์˜ ์ฐจ์ด๋Š” ๋ฐ˜์‚ฌ์œจ ๊ณ„์‚ฐ๋ฐฉ์‹์˜ ์ฐจ์ด์— ๊ทผ๊ฑฐํ•˜๊ฑฐ๋‚˜ ๊ณต๊ทน๋งค์ฒด๋‚ด๋ถ€์—์„œ ์ˆ˜๋ฆฝ์ž์˜ ์ˆ˜ํ‰ ๋ฐ ์—ฐ์ง ๊ถค๋„์œ ์†์˜ ์žฌํ˜„์ •๋„๊ฐ€ ๋‹ค์†Œ ๋ฏธํกํ•˜๊ธฐ ๋•Œ๋ฌธ์ธ ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ด๋ฅผ ๊ฐœ์„ ํ•˜๊ธฐ ์œ„ํ•œ ์ถ”๊ฐ€์ ์ธ ์—ฐ๊ตฌ ๋ฐ ํ™•์ธ ์ˆ˜๋ฆฌ์‹คํ—˜์ด ์š”๊ตฌ๋œ๋‹ค.

Acknowledgements

์ด ๋…ผ๋ฌธ์€ 2014ํ•™๋…„๋„ ๊ฑด๊ตญ๋Œ€ํ•™๊ต์˜ ์—ฐ๊ตฌ๋…„๊ต์› ์ง€์›์— ์˜ํ•˜์—ฌ ์—ฐ๊ตฌ๋˜์—ˆ์Œ. ๋˜ํ•œ, ๋ถ€๋ถ„์ ์œผ๋กœ 2015๋…„ ํ•ด์–‘์ˆ˜์‚ฐ๋ถ€์˜ ์žฌ์›์œผ๋กœ ํ•œ๊ตญํ•ด์–‘๊ณผํ•™๊ธฐ์ˆ ์ง„ํฅ์›์˜ ์ง€์›์„ ๋ฐ›์•„ ์ˆ˜ํ–‰๋˜์—ˆ์Œ(์ข…ํ•ฉํ•ด์–‘๊ณผํ•™๊ธฐ์ง€ ๊ตฌ์ถ• ๋ฐ ํ™œ์šฉ์—ฐ๊ตฌ).

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