Systems and methods with seal elements shaped to efficiently cement casing and seal a hanger in a wellhead housing

A method of operating a wellhead, the method comprising:

• running a hanger with a seal assembly into a wellhead housing, wherein the seal assembly comprises one or more seal elements with a wavy shape along a circumferential axis;
• performing cementing operations while the seal assembly is in a first position in which a first feature defined by the wavy shape is circumferentially aligned with a passage formed in the wellhead to enable a flow of fluid across the seal assembly via the passage;
• and
• after the cementing operations, rotating the seal assembly to a second position in which a second feature defined by the wavy shape is circumferentially aligned with the passage formed in the wellhead to block the flow of fluid across the seal assembly via the passage.

A wellhead, comprising:

• a wellhead housing;
• a passage formed in or along the wellhead housing;
• a hanger configured to support a casing within the wellhead housing;
• and
• a seal assembly positioned about or within the hanger, wherein the seal assembly comprises one or more annular seal elements that define one or more peaks and one or more valleys distributed along a circumferential axis and the seal assembly is configured to rotate within the wellhead housing to circumferentially align at least one valley of the one or more valleys or at least one peak of the one or more peaks with the passage to enable a flow of fluid across the seal assembly via the passage.