Name: evolution of staircase structures in diffusive convection
Uploaded: 2018-09-05T15:30:00
Description: Watch this Scientific Journal Video about Evolution of Staircase Structures in Diffusive Convection at JoVE.com

この作品は、中国の NSF の補助金 (41706033、91752108、41476167)、(2017A030313242 と 2016A030311042) Grangdong NSF の補助金および LTO 補助金 (LTOZZ1801) によって支えられました。

1. ワーキング タンク
注: 実験は長方形タンクで実施です。タンクは、上部と下部のプレートと側壁に含まれます。上部と下部プレートは、めっき表面の銅から成っています。トップ プレートの中で水室があります。電気加熱パッドは、底板に挿入されます。側の壁は透明なプレキシ グラス製です。水槽サイズは Lx 257 mm (長さ)、Lyを = = 65 mm (幅)、Lz</sub...

<ol>
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本稿で詳細な実験的プロトコルは矩形容器内熱塩 DC 階段構造をシミュレートに記載されます。作動流体の初期密度成層は、2 つのタンクのメソッドを使用して構築されます。トップ プレートは、一定の温度と熱流束一定の 1 つ下で保持されます。DC の階段は、生成、発展、没入、消失などの全体の進化プロセスは、影絵を用いた可視化し、高精度プローブにより温度と塩分濃度の差異を記録...

二重拡散対流 (DDC) は、最も重要な垂直混合プロセスのひとつです。それは、層状水の列の垂直方向の密度分布がコンポーネントが異なる分子拡散1をある反対の方向の 2 つ以上のスカラー部品勾配によって制御されるときに発生します。それは広く海洋2雰囲気3、地質学4、天体物理学5、材料科学6冶金7、および建築工学8で発生します。DDC は、世界の海洋のほとんど半分で現在、海洋のマルチ スケール プロセスとも気候変動9に対する重要な効果です。
DDC の主に 2 つのモードがある: 塩の指 (SF) と拡散対流 (DC)。SF は、暖かく、塩辛い水固まり成層環境でクーラー、新鮮な水を覆います。暖かく、塩辛い水は冷たい、新鮮な水の下にある、DC が形成されます。DC の顕著な特徴は、水温・塩分・密度の鉛直分布が階段のようより均一に対流する層と薄く、強く成層界面によって構成されることです。DC は高緯度の海や北極海や南極海などのいくつかの内部の salt 湖で主にオホーツク海、紅海、アフリカのキブ湖10発生します。北極海の流域と永続的な DC 階段上部と深い海11,12が存在します。それは深層海洋上層の混合に重要な影響を及ぼすし、氷の融解、最近海洋コミュニティ13より多くの興味をそそりますに大きく影響があります。
DC 階段構造最初 1969年14で、北極海で発見されました。その、パッドマン ・ ディロン15後、ティンメルマンスら。11、Sirevaag & Fer16周・魯12、ガスリーら。17Bebieva ・ ティンメルマンスは18、およびワイスマンら。19測定垂直方向を含む北極海の異なる流域で DC 階段と対流層とインターフェイス、深さと、階段の総厚さの水平スケール垂直伝で DC プロセスメソ渦と階段構造の時空変遷。シュミットら。20ゾンマーら21は、キブ湖の微細構造プロファイラーを用いて DC 階段を観察しました。彼らは主要な構造機能および DC の熱流束を報告、既存のパラメトリック式で測定した熱フラックスを比較します。コンピューターの処理速度を向上させると DC のシミュレーションが行われている最近、たとえば、インターフェイスを確認する構造と不安定性、インターフェイスを通じて熱伝達層の結合イベント22,23,24。
フィールド観測、海洋学者の海 DC の理解を大幅に強化が、測定は強く中間海洋流れ環境と楽器によって制限されます。たとえば、DC インターフェイスは、非常に小型の垂直方向のスケールをいくつか湖や海で25、0.1 m よりも薄いといくつかの特別な高解像度の器具が必要があります。実験では、DC の基本的な動的・熱力学的法則を探究することに独特な利点を示しています。室内実験と DC 階段の進化を観察、温度と塩分濃度測定、海洋アプリケーション26,27のいくつかのパラメーター化を提案できます。さらに、研究室の実験では、制御パラメーターと条件が容易に調整必要に応じて。たとえば、ターナーは最初 1965 年に実験室で DC 階段をシミュレートし、頻繁に更新され、その場で海洋観測28 で広く使用されて拡散界面熱伝達のパラメーター化を提案.
本稿で詳細な実験的プロトコルと DC 階段を下から加熱成層の食塩水で生成、開発および消失を含むの進化プロセスをシミュレートする説明です。水温・塩分は、影絵を用いた監視されている DC 階段と同様、マイクロ スケール装置によって測定されます。実験のセットアップ、進化プロセス、データ分析、および結果の検討は、詳細で説明されます。初期と境界条件を変えることによって現在の実験設定とメソッドを海洋の水平対流、深海熱水噴火、表層混合層の深化の効果などの他の海洋現象をシミュレートするために使用できます。潜水艦が海洋循環上の地熱です。

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		<tr height="28">
			<td height="28" style="height:28px;width:185px;">Plastic soft tube</td>
			<td style="width:152px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Multiple suppliers</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Direct-current power supply</td>
			<td style="width:152px;">GE Inc.</td>
			<td style="width:119px;">GPS-3030</td>
			<td></td>
		</tr>
		<tr height="32">
			<td height="32" style="height:32px;width:185px;">Matlab</td>
			<td style="width:152px;">MathWorks Inc.</td>
			<td style="width:119px;">R2012a</td>
			<td></td>
		</tr>
	</tbody>
</table>

evolution of staircase structures in diffusive convection

拡散対流 (DC) 密度が 2 つの異なる分子拡散スカラーのグラデーションに反対によって制御されより大きいと、小さい-拡散スカラー勾配が正と負の垂直層状するときに発生します密度分布のための貢献それぞれ。DC は、多くの自然のプロセスと工学的応用、海洋学、天体物理学、冶金などで発生します。海洋の DC の最も顕著な特徴の 1 つは鉛直水温・塩分分布が厚い均一対流層と比較的薄いと高勾配インタ フェース連続ステップの階段のような構造であることです。DC 階段は北極と南極海を中心に、いろいろな海で観察されているし、海洋循環と気候変動に重要な役割を果たします。北極海における上部と深い海の流域と永続的な DC の階段が存在します。DC プロセスは深層海洋上層の混合に重要な影響を及ぼすし、表面の氷の融解に大きく影響があります。実験観測の制限に比べると、そのユニークな利点 dc、動的・熱力学的プロセスを効果的に調べる境界条件と制御のパラメーターを厳密に調整できますのでを示しています。ここでは、詳細なプロトコルと成層の食塩水で満たされた長方形タンクの生成、開発および消失を含む DC 階段構造の進化プロセスをシミュレートする説明です。実験のセットアップ、進化プロセス、データ分析、および結果の検討は、詳細で説明されます。

実験装置の概略図を図 1に示します。そのコンポーネントは、プロトコルのとおりです。主要部品、図 1 aに示すように、詳細な現用戦車は図 1 bに示すように。図 2は、下部 (Tb、赤色の曲線) と (Tt、黒の曲線) トップ プレートの温度変化を示しています。それは 2 つのプレートの温度は?...

Watch this Scientific Journal Video about Evolution of Staircase Structures in Diffusive Convection at JoVE.com

Evolution of Staircase Structures in Diffusive Convection

拡散対流 (DC) は広く自然のプロセスと同種の対流層と成層界面と階段の連続によって特徴付けられる、エンジニア リング アプリケーションで発生します。実験手順、長方形タンクの生成、開発および消失を含む、DC 階段構造の進化プロセスをシミュレートする説明します。

拡散対流における階段形状の進化

Diffusive convection (DC) occurs when the vertical stratified density is controlled by two opposing scalar gradients that have distinctly different ...

This method can be used to explore the key issues in the dynamic processes of diffusive convection staircase structures, such as their generation, development, and disappearance. With the present experimental setup, we can clearly see the evolution of diffusive convection, which is very difficult, if it is not impossible, to observe directly in the ocean. Gather the components of the working tank.These include copper top and bottom plates and an acrylic sidewall assembly. The top plate is electroplated and encloses a water chamber accessible by tubes. It also has places for thermistors.The bottom plate is also electroplated and has slots for thermistors. It contains a heating pad. Use distilled water to carefully clean the copper plates and the acrylic sidewalls.When done, assemble the tank using screws to ensure it is water-tight. This completed tank is 257 millimeters in length and height and 65 millimeters wide. At an optical table, set up a stainless-steel supporting frame.On top of the frame, place an insulating slab. With everything in place, place the assembled tank on the slab. Insert thermistors into the top and bottom plates, and connect them to the data acquisition system.A thermistor monitors the temperature of the plate into which it is placed. Next, move a precision vertical translation stage into place for mounting a probe. Through the top plate, place a micro scale conductivity and temperature instrument sensor into the tank.Fix the instrument to the precision translation stage. Now, set up software for sensor data acquisition and thermistor readings. Return to the tank to adjust the position of the conductivity and temperature sensor.Set the initial position of the sensor at its lowest point, here, 20 millimeters above the bottom of the tank. Then, set the parameters of the motion for the translation stage for the experiment. Use the shadowgraph technique to monitor the experiment.For this, attach a piece of tracing paper on the outside of one side of the tank. On the opposite side of the tank, about five meters away, place a light source. To produce a nearly collimated beam, use a narrow beam LED as a light source.Place a high-speed camcorder about a meter in front of the tracing paper in the beam path. With the lamp and camcorder on, adjust their positions for a clear image. Obtain two identical rectangular tanks for the working fluid.The tanks are the same size as the working tank. Join them at their base with a clamped flexible tube, 10 centimeters in length. Place the two tanks at the same height.Arrange for one tank to have an electric stirrer in it. Next, clamp a flexible 50-centimeter tube into a peristaltic pump. Use the tube to join the tank with the stirrer to the working tank.Fill the tank that has no stirrer with saline solution of 60 grams per kilogram concentration. Fill the other tank with an equal volume of degassed fresh water. Once the tanks are filled, unclamp the connecting tube.Continuously homogenize the mixing water with the electric stirrer. Control the flow rate in the working tank with the peristaltic pump. The working tank takes approximately three hours to fill and be ready for the experiment.For an experiment, use a refrigerated circulator to set the top plate boundary conditions. At the top plate, connect the water chamber to the refrigerated circulator using eight soft plastic tubes. At the circulator, set the temperature for the top plate to the room temperature.Now, connect the bottom plate's heating pad to a DC power supply, and set its power level. Turn on the camcorder to record the flow pattern. Begin monitoring temperature and salinity data.Then, start vertical motion of the sensor. Finally, turn on the refrigerated circulator and the DC power supply to achieve the working fluid boundary conditions. This is an example of a shadowgraph image taken when the top plate is at the room temperature and the bottom plate is being heated.There are three convecting layers in the image, where the fluid density is homogeneous. There are also three interface layers, where large density gradients exist. This intensity fluctuation profile has three peaks that correspond to the interfaces.Here is the evolution of the intensity fluctuation profile in time, which reveals layer generation, development, and disappearance associated with the diffusive convection staircase. The temperature profile and the salinity profile provide other views of the evolution in time of the system. In these profiles, each continuous line represents data collected over 404 seconds.The data sets in the temperature profile are each offset by 1.5 degrees Celsius from the one before. For the salinity profile, each data set is offset by three grams per kilogram from the previous set. This method can also be applied to simulate other phenomenon in oceans, such as global oceanic circulation, mixed layer deepening, and hydrothermal plume eruption.If you want to try this procedure, please do remember to initially adjust the conductivity and temperature sensors to the lowest position of the translation stage to prevent the sensor for crashing on the bottom plate. With the presented results, we can further develop new parameterization of layer thickness, heat flux, and add diffusivity in diffusive convection, which would pave the way for the community of physical oceanography to study the phenomena in the oceanic application.

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