Bottom Loads Research Articles

Gravity/topography admittance inversion on Venus using niching genetic algorithms

We used niching genetic algorithms (NGAs) to invert localized Venus gravity/topography admittance over lowland regions Atalanta and Lavinia Planitiae, as well as volcanic rise Atla Regio for comparison. Assuming both top (topography) and bottom (mantle density anomalies) loads, we calculated theoretical admittance using thin elastic shell models. We inverted admittance for crustal thickness, elastic lithosphere thickness, mantle density anomaly thickness, and ratio (pz) of mantle density anomaly to topographic load. NGA inversion provides an efficient means of finding globally optimal and sub‐optimal solutions. Error analyses of all three regions show that pz is a robust estimate; there is significant trade‐off between elastic lithosphere and mantle anomaly thicknesses, while crustal thickness is ill‐constrained. Optimal models suggest that mantle density anomalies are ∼+1 to 2% underlying lowland regions and ∼−3 to −4% underlying Atla Regio.

Comments on the Structural Design of High Speed Craft

A brief discussion of materials used in the construction of small high speed craft is given along with a history of the calculation of hydrodynamic bottom loads. Calculation methods currently in use are reviewed, including those for added drag in waves, vertical accelerations in rough water, total bottom load, load on each structural member, and the required structural properties of the member. In particular, a discussion of the uncertainty inherent in these methods is presented, as well as a recommendation for a somewhat simpler approach which removes some of the uncertainty, and additional recommendations for the improvement of several details of the procedure.

Comparison of Load Distribution in Two Similar Grain Bins

Wall and bottom loads and the resultant moment of force have been compared for two similar model bins. Corrugated wall bins of 0.6 and 1.2 m in diameter with height-to-diameter ratios of 4 were used in the experiments. The wall and flat bottom of the bins were each supported independently on three load cells to isolate wall and bottom loads. Center and off-center discharge of the bins was tested. The vertical wall load to total grain load and the dimensionless moment found during eccentric discharge were strongly influenced by the difference in the wall friction coefficient resulting from different size corrugations and different kinds of grain. The maximum moment was found for an orifice eccentricity ratio of 0.67 for both bins.

Dynamic Load Response in a Model Bin at the Start of Grain Discharge

The dynamic response of the vertical wall and bottom loads at the start of grain discharge was influenced by wall configuration and filling method for model bins in plug flow. Experiments were conducted with wheat in cylindrical smooth wall and corrugated bins which were 0.6 m in diameter and 2.4 m high. Central spout and sprinkle filling methods were tested. The highest wall load increase was observed for the smooth wall bin when centrally filled. The corrugated wall and sprinkle filling method produced the smallest wall load increase. A peaked response of the dynamic wall load was observed for both bin wall surfaces which were center filled. Two steps of wall load increase after the start of discharge were observed for sprinkle filling of the smooth wall bin, one occurred immediately after orifice opening and the second occurred after 1 to 2 min of discharge.

Loads in Model Grain Bins as Affected by Filling Methods

Measurements of wall and bottom loads in flat-bottom model bins have shown the influence of filling methods and wall surface on wall loads and the static-to-dynamic load shift. Four spout-filling methods, at center and eccentric locations, sprinkle filling, and uniformly filling through an annular ring near the bin wall, were evaluated. Three types of bin walls were tested for each filling method: smooth galvanized steel, corrugated galvanized steel, and smooth steel covered with abrasive cloth. Soft and hard winter wheats were used in the experiments. The static wall load to total grain load ratio (SWL/TGL) and the dynamic-to-static wall load ratio (DSR) were found to be influenced by the filling method. In general, a higher SWL/TGL resulted in a lower DSR. Sprinkle filling produced lower SWL/TGL values on the smooth wall and higher values on the rough and corrugated walls. The ratio of the wall to total grain load at the start of discharge was highest for the first opening of the discharge gate as compared to two successive gate openings (each after 30 min of rest). The filling method and the type of wheat significantly influenced the negative friction force on the smooth wall bin. Negative friction force values were highest for the top filling methods. A negative friction force was not observed for corrugated and rough wall bins.

WALL AND BOTTOM LOADS IN A MODEL GRAIN BIN DURING DISCHARGE

ABSTRACT It was found that elasticity of wheat significantly influences bin wall and bottom loads during discharge. A change in the direction of the resultant friction force against the bin wall was observed in the final stage of discharge. The observed relationship between the resultant friction force and the grain height results from the downward friction force of flowing grain and the upward friction force of the dead zone of the bin.

Dynamic Wall Loads in a Corrugated Walled Model Grain Bin

ABSTRACT MEASUREMENTS of total static and dynamic wall and bottom loads in a corrugated model grain bin 0.91 m in diameter and 3.30 m tall were measured as a function of grain height, grain hopper configuration, and grain discharge rate for corn, wheat and soybeans. The total bin loads were found to vary as a function of grain, grain height, and grain hopper configuration.

Studies of the seasonal variation of the suspended matter of the Menai Straits II. Mid stream data

Surface and bottom inorganic and organic suspended loads in the Menai Straits were correlated with those hydrographical and meteorological elements which were considered to have an influence on them. Surface inorganic loads correlated significantly with tidal range, water temperature (negatively) and run of wind. This latter factor did not correlate so highly with the bottom inorganic fraction. Significant correlations were evident between surface and bottom organic loads and tidal range. The correlations between turbidity, as measured by Secchi disc, and the suspended sediment load were also investigated.

Investigation of Silo Loads in Measuring Models

The test results described are a portion of a current comprehensive series of investigations. No attempt is made to produce the values for wall frictional and bottom loads, which were measured simultaneously with horizontal pressure. Data obtained from the measurements prove that, although standard specifications on the calculation of silo loads are incorrect in some details, adherence to these loading data will not damage silos.