計算流體力學應用於植物工廠草莓自動授粉與半結球萵苣葉燒防止之探討

Abstract

本研究透過計算流體力學 (Computational Fluid Dynamics, CFD) 軟體模擬草莓 (Fragaria × ananassa Duch.) 與奶油萵苣 (Lactuca sativa var. capitata) 栽培空間的流場與溫度場分布，旨在為草莓自動授粉與半結球奶油萵苣葉燒 (Tip-burn) 問題提供對策。草莓栽培採用由CFD模擬得出的較佳給風方式，比較人工授粉與自動授粉之果實授粉率；奶油萵苣栽培採用三個不同流場設計進行試驗，探討透過栽培探討模擬結果對於葉燒程度之影響。 草莓流場模擬以風管中心軸相對於層架長邊水平軸旋轉30度，搭配層架左側軸流扇之流場具有最佳的風速分布，風速大於0.5 m·s-1的占比為85.85 %。依此流場設計進行栽培，層架內單層有五株作物，每株採收22 ~ 24顆果實，果實之授粉程度達80 % 以上。 半結球萵苣流場模擬結果顯示以兩支風管 (管內風速11 m·s-1) 可有最大占比 (45.24 %) 的適當葉冠層風速 (0.3 ~ 1 m·s-1)，溫度場模擬結果顯示平均溫度為 293.9 K (20.8°C)，略低於模擬之初的環境溫度 (294 K)，栽培後植株地上部鮮重為 123 g.plant-1且均無葉燒發生。垂直流場 (風管處理組) 可有效降低葉燒程度，優於側向流場 (軸流風扇處理組)。高風速可促進蒸散發生，利於散熱，但過高的風速則會使地上部鮮重降低。以較低的風速 (4.5 m·s-1) 進行栽培且改採間歇方式送風，地上部鮮重 (143.6 g·plant-1) 可提高，但葉燒程度也略為增加 (0.2)。 本研究以CFD模擬探討層架內氣流與溫度的分布情形，藉此找出合適的流場設計，採用風管及軸流扇的給風方式進行草莓自動授粉與奶油萵苣之栽培，前者提供一個可行的方案，作為室內草莓授粉之選項；後者可降低葉燒程度，提高其生產效能並提升其賣相。

This study used Computational Fluid Dynamics (CFD) to simulate the airflow and temperature distribution within the cultivation space of strawberry (Fragaria × ananassa Duch.) and semi-head lettuce (Lactuca sativa var. capitata). The objective was to address the issues of automated pollination in strawberries and tip-burn in Boston lettuce. For strawberry cultivation, the optimal airflow configuration obtained through CFD simulation was utilized to compare the pollination rates between hand and automated methods. In the case of semi-head lettuce, three different flow field designs were tested to explore the impact of simulation results on tip-burn severity during cultivation. In the strawberry flow field simulation, rotating the wind duct center axis 30 degrees relative to the long side of the shelf's horizontal axis and coupling it with the flow field generated by the axial fan on the left side of the shelf yielded the optimal wind velocity distribution. The proportion of wind velocity exceeding 0.5 m·s-1 was 85.85 %. Cultivation was carried out based on this flow field design, with a single layer of five plants per shelf. Each plant yielded around 22 to 24 fruits, and the pollination rate of the strawberries exceeded 80 %. The flow field simulation results for semi-head lettuce indicated that using two wind ducts (with an internal wind velocity of 11 m·s-1) achieved an appropriate canopy wind speed distribution with the highest proportion (45.24 %) falling within the range of 0.3 to 1 m·s-1. The temperature field simulation results reveal an average temperature of 293.9 K (20.8 °C), slightly lower than the initial environmental temperature in the simulation (294 K). After cultivation, the shoot fresh weight of the plants was 123 g·plant-1, and no instances of tip-burn were observed. The vertical flow field (wind duct treatment) effectively reduced tip-burn severity, outperforming the lateral flow field (axial fan treatment). Higher wind velocity facilitated transpiration and cooling, yet excessive wind velocity led to a reduction in shoot fresh weight. Employing lower wind velocity (4.5 m·s-1) for cultivation and adopting intermittent airflow delivery increased shoot fresh weight (143.6 g·plant-1) but slightly elevated tip-burn severity (0.2). This study used CFD simulation to explore the distribution of airflow and temperature within shelves. The wind duct and axial fan methods were used for the cultivation of strawberries with automated pollination and semi-head lettuce. The former provided a feasible solution as an option for indoor strawberry pollination, while the latter reduced tip-burn severity, enhanced production efficiency, and improved presentation.