Changes between Version 75 and Version 76 of WikiStart


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Timestamp:
Sep 20, 2016, 5:19:31 PM (4 years ago)
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peakall3je
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  • WikiStart

    v75 v76  
    105105
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    107 
    108 [[PageOutline]]
    109 
    110 = '''Project Name''' =
    111 ||Infrastructure||CNRS_Coriolis||
    112 ||Project (long title)||Coriolis and Rotational effects on Stratified Turbulence||
    113 ||Campaign Title (name data folder)||16CREST||
    114 ||Lead Author||Jeffrey Peakall||
    115 ||Contributor||Stephen Darby, Robert Michael Dorrell, Shahrzad Davarpanah Jazi, Gareth Mark Keevil, Jeffrey Peakall, Anna Wåhlin, Mathew Graeme Wells,   Joel Sommeria, Samuel Viboud||
    116 ||Date Campaign Start||12/09/2016||
    117 ||Date Campaign End||21/10/2016||
    118 
    119 [[BR]]
    120 
    121 = 1 - Objectives =
    122 
    123 Our primary objective is to measure detailed turbulence distributions within channelised gravity currents, as a function of Coriolis forces, concentrating on: i) the bottom boundary layer, ii) redistribution of turbulence within bends, and, iii) redistribution of turbulence at the interface between the gravity current and the ambient. These datasets will enable existing theory on the presence and influence of Ekman boundary layers to be tested, with important implication for the basal shear stress distributions, erosion, and the evolution of channels. These data on the distribution of turbulence will then be applied to i) examine the turbulence distribution in straight channels, ii) provide an analysis of secondary flow and associated turbulence around bends for the first time, and an assessment of how channelized flows alter as a function of Rossby numbers and therefore latitude, iii) assess how the morphodynamics of submarine channels vary as a function of the Rossby number, iv) explain the observed patterns of submarine channel sinuosity with latitude (Peakall et al., 2012; Cossu and Wells, 2013; Cossu et al., 2015), and, v) incorporate the entrainment data into numerical models of submarine channels, in order to address the unanswered question of how these flows traverse such large-distances across very low-angle slopes (Dorrell et al., 2014).Our primary objective is to measure detailed turbulence distributions within channelised gravity currents, as a function of Coriolis forces, concentrating on: i) the bottom boundary layer, ii) redistribution of turbulence within bends, and, iii) redistribution of turbulence at the interface between the gravity current and the ambient. These datasets will enable existing theory on the presence and influence of Ekman boundary layers to be tested, with important implication for the basal shear stress distributions, erosion, and the evolution of channels. These data on the distribution of turbulence will then be applied to i) examine the turbulence distribution in straight channels, ii) provide an analysis of secondary flow and associated turbulence around bends for the first time, and an assessment of how channelized flows alter as a function of Rossby numbers and therefore latitude, iii) assess how the morphodynamics of submarine channels vary as a function of the Rossby number, iv) explain the observed patterns of submarine channel sinuosity with latitude (Peakall et al., 2012; Cossu and Wells, 2013; Cossu et al., 2015), and, v) incorporate the entrainment data into numerical models of submarine channels, in order to address the unanswered question of how these flows traverse such large-distances across very low-angle slopes (Dorrell et al., 2014).
    124 
    125 [[BR]]
    126 
    127 = 2 - Experimental setup: =
    128 
    129 [[Image(Set_up_drawing.jpg)]]
    130  
    131 
    132 
    133 == 2.1 General description ==
    134 
    135 2.1 General description
    136 A channel model is positioned within the Coriolis facility. The channel model consists of an initial tapered input section with a honeycomb baffle for flow straightening and turbulence control, a 3.2 m straight channel section, and two bends with a mid-channel radius of 1.5 m. The channel is made of acrylic and is 60 cm wide and 50 cm high; the sinuous section has a sinuosity of 1.2. The slope is 3/50 radians (3.5 degrees, 6% gradient) and the channel terminates 10 cm off of the floor. Saline fluid is pumped into the top of the channel, forming a gravity current, which flows along the channel, and off the end. The basal 10 cm of the flume operates as a sump for the denser saline fluid to accumulate. In turn, this fluid can be drawn down in one of two ways: i) whilst recirculating the fluid, though this is limited to 20 $m^3$/hr (5.55 l/s), and ii) through emptying to the drain, in which case any flow rate is possible.
    137 Two long metal rails are positioned to either side of the channel model across the full width of the flume. These carry a computerized gantry, which can be positioned at any point along the channel. The gantry itself contains the controls for two Schneider slides, one orientated transverse to the model, and the other connected slide, orientated in the vertical. Thus the system enables xyz control.
    138 
    139 
    140 == 2.2 Definition of the co-ordinate system ==
    141 
    142 
    143 == 2.3 Fixed Parameters ==
    144 
    145 ||'''Notation'''||'''Definition'''||'''Values'''||'''Remarks'''||
    146 || $Q_0$ || Input Density || $12 \ ls^-^1$ || ||
    147 || $\Delta\rho$ || Density Difference || $20 \ kg \ m^-^3$  || ||
    148 || $W$ || Channel Width || $0.6 \ m$ || ||
    149 || $\nu$ || Viscosity || $10^-^6m^2s^-^1$ || ||
    150 || $S$ || Slope|| $3.5^{\circ}$ || ||
    151 
    152 
    153 == 2.4 Variable Parameters ==
    154 
    155 ||'''Notation'''||'''Definition'''||'''Unit'''||'''Initial Estimated Values'''||'''Remarks'''||
    156 || $\Omega$ || Rotation Rate || $rads^-^1$ || -0.18 - 0.15 || ||
    157 || $H_w$ || Water Depth || $m$ || 1-1.1 || ||
    158 || $Q_o_u_t_p_u_t$ || Output Flow Rate || $ls^-^1$ || 5.5 - 17 || ||
    159 || $k$ || Roughness || - || -  || ||
    160 
    161 == 2.5 Additional Parameters ==
    162 
    163 ||'''Notation'''||'''Definition'''||'''Unit'''||'''Initial Estimated Values'''||
    164 || $h$ || Depth of gravity current || $m$ || 0.1 ||
    165 || $U$ || Mean downslope velocity || $m^s^-^1$ || 0.1-0.15 ||
    166 || $\delta$ || Thickness of Ekman boundary layer || $mm$ || ~10 ||
    167 || $R$ || Radius of curvature || $m$ || 1.5 ||
    168 
    169 == 2.6 Definition of the relevant non-dimensional numbers ==
    170 
    171 Flow Reynolds number across the obstruction, $Re = Uh/\nu$.
    172 
    173 Densimetric Froude number, $Fr = U/(g'h)^{1/2}$, $g' = g(\Delta\rho)/\rho_0$.
    174 
    175 Rossby number, $Ro = U/fW$.
    176 
    177 Canyon number, $\beta = sW/\delta$.
    178 
    179 [[BR]]
    180 
    181 
    182 = 6 - Table of Experiments: =
    183 
    184 ||'''Run Name'''||'''Downstream (x)Position'''||'''Density Excess '''||'''Input flow'''||'''Rotation Rate'''||'''Initial Water Depth'''||'''Outflow Rate'''||'''Run Time'''||'''ADV Dwell Time'''||
    185 || ||  || $(kg \ m^-^3)$ || $(ls^-^1)$ || $(rad \ s^-^1)$ || $(m)$ || $(ls^-^1)$ || $(Minutes)$ || $(s)$ ||
    186 ||fixstr1_1909A|| xx || 20 || 12 || 0 || 1 || 5.5 || 30 || continuous ||
    187 ||fixstr1_2009A|| xx || 20 || 12 || 0 || 1 || 5.5 || 20 || 60 ||
    188 ||Smooth_3|| 2 || 20 || 12 || 0 || 1 || 5.5 || 20 || 60 ||
    189 ||Smooth_4|| 3 || 20 || 12 || 0 || 1 || 5.5 || 20 || 60 ||
    190 ||Smooth_5|| 4 || 20 || 12 || 0 || 1 || 5.5 || 20 || 60 ||
    191 ||Smooth_6|| 1 || 20 || 12 || 0 || 1 || 5.5 || 20 || 30 ||
    192 ||Smooth_7|| 3 || 20 || 12 || 0 || 1 || 5.5 || 20 || 30 ||
    193 ||Smooth_8|| 4 || 20 || 12 || 0 || 1 || 5.5 || 20 || 30 ||
    194 ||Smooth_9|| 2 || 20 || 12 || 0 || 1 || 12.0 || 60 || 30 ||
    195 
    196 [[BR]]
    197 
    198 = 7 - Diary: =
    199 = fixstr1_1909A - 19/09/2016 =
    200 
    201