Washdown flush toilet

A washdown flush toilet comprising:

• a bowl part configured to receive waste, and
• a water discharge trap conduit connected to a lower portion of the bowl part,
• wherein
• the water discharge trap conduit includes:
• an inlet pipe part whose one end is continuous or connected to the lower portion of the bowl part;
• a trap ascending pipe part whose one end is continuous or connected to the other end of the inlet pipe part and which forms an ascending flow channel;
• and
• a trap descending pipe part whose one end is continuous or connected to the other end of the trap ascending pipe part and which forms a descending flow channel,
• with regard to a cross section perpendicular to a flow direction of the ascending flow channel, a portion on a downstream side of the ascending flow channel is provided with an enlarged part which has a cross section area larger than that on an upstream side of the ascending flow channel, and
• a downstream end of the ascending flow channel and/or an upstream side of the descending flow channel is provided with a shrunk part which has a cross section area smaller than that on the upstream side of the ascending flow channel,
• with regard to the cross section perpendicular to the flow direction of the ascending flow channel, at least a portion at a central region in a right and left direction of a top surface of the enlarged part of the ascending flow channel has a convex upward shape,
• with regard to the cross section perpendicular to the flow direction of the ascending flow channel or the descending flow channel, at least a portion at a central region in a right and left direction of a top surface of the shrunk part has a convex upward shape, and
• a bottom surface from the enlarged part to the shrunk part has a constant horizontal cross section shape,
• the convex upward shape at the central region in the right and left direction of the top surface of the enlarged part has a curvature greater than a curvature at a central region in the right and left direction of the bottom surface of the enlarged part,
• with regard to a cross section perpendicular to a flow direction of the enlarged part, a gap between right and left surfaces of the enlarged part is widened from the bottom surface of the enlarged part toward the top surface of the enlarged part, and
• the trap descending pipe part has a region that extends diagonally downward, whose bottom surface is in a straight shape as seen from a lateral direction.