# Numerical Simulation and Parameter Optimization of Air Slide Based on CFD-DEM
## 1 Introduction  
In grain processing operations, material transportation constitutes a critical component. The ongoing increase in wheat production and advancements in milling technology have made transportation efficiency enhancement a key research focus. Currently, flour transportation primarily employs two methods: screw conveyors and pneumatic pipeline systems. Screw conveyors, as traditional mechanical transport devices, frequently cause material degradation and mechanical wear during operation. Pneumatic pipeline systems utilize high-velocity airflow (reaching up to 15 m/s) to suspend and propel flour particles, but this dilute-phase conveying mode results in low transportation efficiency and high energy consumption. In contrast, air slides only require low-speed airflow to fluidize the flour, which then flows under gravity, significantly reducing particle-equipment collisions and wear while dramatically lowering energy consumption. Additionally, this system enables long-distance transportation with multiple discharge points. Due to these advantages, air-slide conveyors have found extensive applications across various industries, including chemical engineering, building materials, and coal processing. Over the past decade, powder transportation has shifted from high-speed dilute-phase conveying to low-velocity dense-phase conveying, significantly increasing throughputwhile reducing energy consumption [1]. However, due to the highly concentrated and turbulent nature of dense-phase powder flow, research in this area remains challenging [2]. Consequently, gas-solid coupled simulation has become a primary method for studying dense-phase powder conveying [3; 4]. Leveraging the transient simulation capabilities of computational models, researchers can effectively predict the time-dependent distribution characteristics of powder flow and obtain precise data that are difficult to measure experimentally [5]. Current gas-solid coupled simulation studies primarily focus on pneumatic pipeline conveying, where simulation models are established based on material concentration [6; 7]. By investigating empirical models for minimum conveying boundaries, researchers can accurately predict blockage conditions [8]. Conveying simulations enables precise determination of powder distribution density at different locations within the system, helping to analyze the root causes of blockages [9]. Additionally, by establishing particle-wall collision models, researchers can evaluate equipment wear and material degradation, optimizing designs to extend service life [10; 11]. Real-time monitoring of conveying rates, combined with gas-solid interaction mechanisms, further enhances transportation stability [12; 13]. In the study of gas-solid coupling simulation for wheat flour, the selection of turbulence models constitutes a critical factor affecting simulation accuracy. The working principle of air-slide conveyors resembles that of fluidized beds, where the k-\(\epsilon\) model has been widely adopted for fluidized bed simulations [14]. As a two-equation model, it offers high computational efficiency and broad applicability [15; 16]. [PERSON] effectively predicted dust explosion risks by employing the CFD-DEM method to examine difficult-to-measure characteristics such as particle concentration in conveying equipment [17]. [PERSON] investigated the phenomenon of bubbling by using DEM-CFD simulations with different sizes of particles [18]. This study revealed different types of fluidization regimes as stated in the literature. [PERSON] studied the phenomenon of minimum fluidization by using DEM-CFD simulations with different sizes of particles [19]. [PERSON] developed a novel drag force model using CFD-DEM to analyze particle breakage and aggregation phenomena in fluidized beds [20]. While significant progress has been made in the research on fluidized conveying of inorganic powders such as mineral powders, studies specifically addressing wheat flour transportation in air slides remain scarce.